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ajkst1
Jan 18, 2005, 12:23 AM
I'm taking a class at my university and my professor claims that 800 mhz (AMD Opteron) is the fastest front side bus in production. I know better than that because the G5's FSB is equal to half the clock speed of the processor. What is the actual front side bus speed, i.e. what are people actually getting in real world use vs. laboratory testing. He doesn't want Apple marketing nonsense (I showed him that already), he wants technical details and proof (screenshots? :)) that the FSB of a G5 is equal to half the clock speed of the processor.

HELP ME WIN THIS ONE GUYS!

Timelessblur
Jan 18, 2005, 12:44 AM
it a really good question because it where the number is taken from can greatly effect what it is

For example I have a AMD64 3000 in my computer. The mobo is telling my the front side bus is at 200mzh (so does AMD stating that is there FSB number) but that number is taken earily then where it is recored in a P4 chances are the apples does the same so I dont really buy apple number. AMD number is taken from where the data is going both to the ram nad processor so it is running at 200mhz (PPC3200 ram before it his the mulitplyer to up it to 400mhz).

Now if you take the number from the same spot apple and Intel take it the AMD64 are running at 1.6ghz fsb but the AMD64 dont have a standard frount side bus since there memory control modle is integreted into the CPU it self. Something only they have which really up the speed. If the Optron is running on sock 754, 939 or 940 (sorry I can not remeber what the ops run on off the top of my head) then I think it has the ingteted memory modle as well and in reallity it running at 1.6ghz if you want to ajusted it to the what apple and Intel use.

I am sorry but in relaielyt you going ot loose this one. AMD optron and 64 line have a much faster memory control (FSB more or less) than any one else and it faster than apple and Intel.

Mav451
Jan 18, 2005, 12:54 AM
I don't think its actually half the FSB, but you also need to remember that FSB doesn't always translate directly to more performance.

Anyway, in the 939 socket chips, the 200Mhz "FSB" is multiplied by the HTT multiplier (defaulting at 5x), while 754 socket chips are 200Mhz "FSB" with a 4x HTT multiplier.

Comparing P4's to the 939's or the 754, they both could have a theoretical "800FSB" or "1000FSB", but the 754's, even at a much lower clock speed, the AMD chips will beat Intel chips with the same "FSB". That is, if you are comparing CPU performance from a FSB perspective.

That said, you could then move to comparing memory bandwidth as another method for comparing FSBs, for example, but then A64 will win hands down b/c of its inherently reduced latencies. Is there a way of comparing FSBs fairly? If you had a I/O chipset benchmark, that is compiled and tested fairly on both sides, perhaps, but comparing PC to PC is hard enough. Comparing PC to Apple only makes this even more of a grey area.

Timelessblur
Jan 18, 2005, 01:03 AM
also remember how much BS there is in marketing the FSB. and everything else. Realtiy is Apple is starting to get into the famus Mhz myth and starting to almost validated it now. Remeber there is the thing call the mhy myth and there currently is really only one complain not playing into it. Yes it is AMD. they dont brag about there Mhz of there chips. Apple promised 3ghz chips (failed but they are trying) and now are trying to brag about there mhz.

There is a lot more stuff that factors into the speed of a computer

Sun Baked
Jan 18, 2005, 01:19 AM
Why are you looking here, you should be looking at the IBM site for documentation.

Specifically one of the in depth manuals on the PPC970...

970FX_user_manual_v1.41.pdf (http://www-306.ibm.com/chips/techlib/techlib.nsf/techdocs/AE818B5D1DBB02EC87256DDE00007821/$file/970FX_user_manual_v1.41.pdf)

But it does run at half the clock, and is a variant of IBM's elastic bus -- using two 32-bit unidirectional buses.

psycho bob
Jan 18, 2005, 01:48 AM
I don't think when Steve said they would be at 3GHz it was a case of bragging. Of all the CPU makers it has only ever been Intel who have had the figures plastered around. Any PC owner with sense and some idea of what really goes on in the industry would buy AMD processors. Even AMD however were forced to call there processors after the equivalent speed compared to the P4 ie; Athlon 2400 etc. Now Intel have backed themselves in to a corner and have had to move away from naming their CPU's after their speed because they just aren't getting the gains they used to.
Current P4 designs have a FSB's of 800 and 1066MHz, these DDR buses are quad pumped so are actually only 200MHz (in the case of the 800MHz). If someone can explain the 'pumping' principal please do.
The Apple DDR buses on the G5 are double pumped so the true FSB of the dual 2.5 is 625MHz far faster than that of the Pentium 4.
Working out the AMD Athlon 64 FX's FSB is rather harder as someone has pointed out already. AMD love quoting figures in MTps or mega transfers per second. All I can tell you there fore is that AMD were scheduled to release a 1GHz FSB CPU at the start of 2004. From the technical sheets I've managed to see I think they are still at the 1GHz mark and by the looks of it it is double pumped like the G5 so the actual non DDR speed is 500MHz.
The major advantage the with the Athlon 64 design is the on chip memory controller negating the need to have such extreme bus speeds as RAM content can get to the CPU's faster than in the G5 design.
In many ways, memory controllers asside, the AMD and IBM/Apple designs are actually very similar both using Hypertransport technology as a way of increasing throughput.
Strictly speaking then I would say that the G5 does indeed have the fastest FSB, but the award for most efficient and there fore over all fastest would go to the AMD Athlon.

psycho bob
Jan 18, 2005, 02:03 AM
A bit more research;
http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_8826_9014,00.html
In the Opteron the memory FSB is the same as the processor as AMD are quick to point out. But the FSB for other data throughput to the processors is much slower as discussed above. So really it depends on what your teacher meant by FSB, if he meant from RAM then he is right, if he meant all data then you are correct.
The interesting thing about the the Opteron is how it scales up to 4 CPU systems. The bandwidth is dedicated for each CPU so while comparing a 1 CPU Opteron to a single G5 gives pretty similar results when you start scaling with 2 or more the bandwidth figures for the AMD system take a huge lead. Where the G5's FSB does excel is CPU to CPU transfers here there isn't a main stream system to touch it.

solvs
Jan 18, 2005, 03:41 AM
I can't really elaborate much more than they have already, just simplify it.

AMD had DDR FSBs. So the first Athlon was 100MHz double pumped to 200MHz. Like with DDR RAM, rising and falling. The latest was 400, so 200 DDR. The current 64-bit CPUs do have integrated, on chip FSBs... but as said how fast they talk to the memory is a different matter. If you're talking just regular FSB, it is full speed. Up to 2.6 I believe.

The P4 is quad-pumped. 1066 is actually 266 x4. Like RAMBUS.

The G5 is half the CPU speed on the high end. It's not marketing speak, that's how fast it is. The G5 in the eMac uses a slower FSB for lower heat. But the 2.5 uses a 1.25GHz FSB. Whether that makes it faster than what AMD has to offer is debatable. The G5's bus is what it is, and the AMD's is full speed, but there are caveats as to how fast it talks to the RAM.

I'm afraid it's an arguement neither of you can win because there are too many other variables, so you might want to just let it go. Since the fastest standard RAM at this point is dual-channel 400MHz (200 DDR x2, x2 for an effective 800), DDR2 notwithstanding, it probably doesn't matter either way anyway.

psycho bob
Jan 18, 2005, 05:31 AM
I can't really elaborate much more than they have already, just simplify it.

AMD had DDR FSBs. So the first Athlon was 100MHz double pumped to 200MHz. Like with DDR RAM, rising and falling. The latest was 400, so 200 DDR. The current 64-bit CPUs do have integrated, on chip FSBs... but as said how fast they talk to the memory is a different matter. If you're talking just regular FSB, it is full speed. Up to 2.6 I believe.

The P4 is quad-pumped. 1066 is actually 266 x4. Like RAMBUS.

The G5 is half the CPU speed on the high end. It's not marketing speak, that's how fast it is. The G5 in the eMac uses a slower FSB for lower heat. But the 2.5 uses a 1.25GHz FSB. Whether that makes it faster than what AMD has to offer is debatable. The G5's bus is what it is, and the AMD's is full speed, but there are caveats as to how fast it talks to the RAM.

I'm afraid it's an arguement neither of you can win because there are too many other variables, so you might want to just let it go. Since the fastest standard RAM at this point is dual-channel 400MHz (200 DDR x2, x2 for an effective 800), DDR2 notwithstanding, it probably doesn't matter either way anyway.

Apparently there is DDR 500 now as well so dual channel would allow for 1000MHz. DDR2 is faster but currently you pay through the nose for it.
Maybe I misread the AMD documents but I thought it was the RAM which got the full processor speed FSB while the rest of the components got a much slower bandwidth around 1000MHz.

carlos700
Jan 18, 2005, 07:14 AM
The Frontside Bus is actually the speed in which you multiply the multiplier to get the clock speed.

example: 200MHz FSB times 10x multiplier equals 2GHz processor

when labeling the FSB, if they are double or quadruple-pumped they will put that instead. It should be actually labeled as MT/s or megatransfers.

On Intel's and AMD's PDF spec sheets they will label it as 800 MT/s or 2000 MT/s

AMD has the fastest bus at 2x1000 MHz or 2000 MT/s

Timelessblur
Jan 18, 2005, 07:36 AM
also rememeber the FSB is taken from the apple after it hit the first multipleir. Because if you take a look at the mobo speed for the FSB of intel is really at 200mhz (limited by the ram speed). Hmm who would of known stuff about overclocking would come in handy

Since the apple computer are using PC3200 ram it fsb speed is going to be set at 200mhz. PC3200 ram is only designed to take a fsb speed of 200mhz the ram it self has a 2x mutiplier built into it to up it to 400mhz. So other the fsb on the apple computers is after the first mulitply that ups it to half the reported clock speed. then it hits anthere 2x mulitplier to go up to the cpu reportec clock speed.

slooksterPSV
Jan 18, 2005, 08:16 AM
Wow I learned something, but like they said, too many variables to calculate in. Now who said that AMD would beat Intel, even if they were the same FSB speed? - He obviously knows his stuff then. Everyone thinks Intel's faster because it has Hyper-Threading Technology (HTT), but AMD is because of its Hyper-Transport Technology (HTT) and lets not forget the 64KB & 128KB L1 Cache... hmm... who else does that.... oh yeah Apple =D. While Intel only has a meezly (I know I spelled that wrong) 32KB (12 for data, 20 for instruction or is it vice-versa). AMD's is 32 & 32 and 64 & 64 data and instruction, respecitvely. While I don't know how IBM allocates Apple's L1 Cache for their processors.

I read that somewhere that the Cache doesn't run at full speed but half on Apple processors, is that true? And does it detract or add to performance? I know AMD's and Intels cache run at full speed, but yeah. I'll check back laterz.

Hodapp
Jan 18, 2005, 08:49 AM
Steve Jobs told me the PowerMac G5 was the fastest computer in the world. :mad:

I feel like such a fool.

crazzyeddie
Jan 18, 2005, 08:54 AM
The G5 (970FX) uses 64k Instruction + 32k data L1 cache, along with 512k L2 per processor. The "old" G5 (970) uses 64k L2 (32k data, 32k Instruction). Those caches are all running at processor speed.

Opteron and Athlon XP use a full 128k L2 and 512k L2 of the Athlon XP or 1MB L2 on the Opteron, but I'm not sure of the speeds.

Mord
Jan 18, 2005, 09:23 AM
only on the older g4's with external l2 cache like the 7400/7410 and external l3 cache with the 745x ran as less than the cpu speed.

MacBandit
Jan 18, 2005, 09:26 AM
Everyone here is talking as if the FSB only communicates to the System RAM. The FSB speed is the speed that it communicates from the CPU to the System controller on a Mac at least. From the system controller the speed is at whatever level the individual components communicate at. The advantage of having a FSB many many times faster then any one component is the lack of bottlenecks. All these components communicate to the system controller at the same time and then all the data is piled into the FSB channel. The faster the FSB the faster that group of data moves through without building up a que.

Timelessblur
Jan 18, 2005, 09:40 AM
Everyone here is talking as if the FSB only communicates to the System RAM. The FSB speed is the speed that it communicates from the CPU to the System controller on a Mac at least. From the system controller the speed is at whatever level the individual components communicate at. The advantage of having a FSB many many times faster then any one component is the lack of bottlenecks. All these components communicate to the system controller at the same time and then all the data is piled into the FSB channel. The faster the FSB the faster that group of data moves through without building up a que.


The reason we are using the ram as the FSB is the FSB is what is used for the CPU to commicated with the rest of the sysstem yes. Also the FSB commmicated with the system ram. I could go in and start explain the diffent parts. Just the FSB part is the one the commicateds with the ram and CPU. Prouble is you push the FSB to high *aka over 200mhz it is going to make the system unstable because the ram can not handle it. PC3200 ram is not designed to run over 400 mhz after the multiplier (2X200mhz=400mhz) to go higher than that a divider needs to be put on the fsb for the ram.

Start looking into over clocking and when the fsb is starting to be pushed past 250mhz the cooling on it starts running into problems. when people Watercool there system some of it goes FSB to keep that from over heating.

wrldwzrd89
Jan 18, 2005, 10:16 AM
The reason we are using the ram as the FSB is the FSB is what is used for the CPU to commicated with the rest of the sysstem yes. Also the FSB commmicated with the system ram. I could go in and start explain the diffent parts. Just the FSB part is the one the commicateds with the ram and CPU. Prouble is you push the FSB to high *aka over 200mhz it is going to make the system unstable because the ram can not handle it. PC3200 ram is not designed to run over 400 mhz after the multiplier (2X200mhz=400mhz) to go higher than that a divider needs to be put on the fsb for the ram.

Start looking into over clocking and when the fsb is starting to be pushed past 250mhz the cooling on it starts running into problems. when people Watercool there system some of it goes FSB to keep that from over heating.
That description is accurate for anything that isn't based on the PowerPC G5. The G5 is different. Unlike other computers, the G5's FSB to CPU multiplier is fixed regardless of the CPU speed. This means that, as shown in Apple's PowerMac line, the faster the CPU (1.8 GHz to 2.0 GHz), the faster the system bus (450 MHz to 500 MHz). However, this bus is DDR, so it effectively doubles its speed (900 MHz to 1000 MHz). Also, the RAM speed is not hard-locked to the system bus speed anymore - it communicates with the system bus as fast as it is able to (with 200 MHz DDR RAM in a dual channel configuration, this speed is 4 times the RAM speed - 800 MHz). It is true that the system bus speed and the RAM speed no longer match under this configuration, but as it turns out, this is desirable due to additional latency accessing the RAM with this configuration (no, I don't know where the additional latency comes from).

For more information regarding this topic:

Ars Technica article on the PPC 970 part 1 (http://arstechnica.com/cpu/02q2/ppc970/ppc970-1.html)
Ars Technica article on the PPC 970 part 2 (http://arstechnica.com/cpu/03q1/ppc970/ppc970-0.html)

psycho bob
Jan 18, 2005, 01:36 PM
Please remember the original question was just about FSB not the memory aspect only. AMD wins the RAM to CPU FSB (2+GHz) but the speed with which other parts communicate such as processor to processor is slower. Apple does have the fastest FSB at least on paper for all general computing activities (bar RAM transfer).
For those discussing RAM as a side issue also remember that the dual channel aspect of the G5's memory controller means that the effective FSB for memory is essentially 800MHz, or 400MHZ before the 2x DDR multiplier. The faster the RAM they use the faster the transfer will be so they could in theory use PC2-5300 (DDR2-667) which in dual channel operation would give 1.334GHz. The problem here is without the onboard memory controller seen in the AMD processors the FSB will become a bottle neck once again, albeit only in extreme cases.
Ideally once apple release the 3GHz+ G5 this will no longer be an issue and they can upgrade the memory they use. The problem is, as pointed out, AMD can state all they like that the CPU can access RAM at processor clock speeds but the RAM just can't keep up so the technology is essentially wasted especially as I know of no AMD motherboard which will support the fastest DDR2 standards. If you ignore latency issues the G5 setup is the most practical for everyday computing. If IBM add the fabled on chip memory contoller then it is no bad thing but I can't forsee any anormous gains compared to what we have now.

Timelessblur
Jan 18, 2005, 03:26 PM
Please remember the original question was just about FSB not the memory aspect only. AMD wins the RAM to CPU FSB (2+GHz) but the speed with which other parts communicate such as processor to processor is slower. Apple does have the fastest FSB at least on paper for all general computing activities (bar RAM transfer).
For those discussing RAM as a side issue also remember that the dual channel aspect of the G5's memory controller means that the effective FSB for memory is essentially 800MHz, or 400MHZ before the 2x DDR multiplier. The faster the RAM they use the faster the transfer will be so they could in theory use PC2-5300 (DDR2-667) which in dual channel operation would give 1.334GHz. The problem here is without the onboard memory controller seen in the AMD processors the FSB will become a bottle neck once again, albeit only in extreme cases.
Ideally once apple release the 3GHz+ G5 this will no longer be an issue and they can upgrade the memory they use. The problem is, as pointed out, AMD can state all they like that the CPU can access RAM at processor clock speeds but the RAM just can't keep up so the technology is essentially wasted especially as I know of no AMD motherboard which will support the fastest DDR2 standards. If you ignore latency issues the G5 setup is the most practical for everyday computing. If IBM add the fabled on chip memory contoller then it is no bad thing but I can't forsee any anormous gains compared to what we have now.

You are wrong on the ram speed. it is under 250mhz. Take the ram speed and divid it by 2. The fast out there is 566mhz ram which is only 233mhz.(it is 233*2) it is 233mhz before it hits the DDR2 2x multplier.

As for DDR2 mobo supported by AMD a few socket 940 and 939 supported itor will soon/ 754 doesnt not and never will because it does not have the bandwith for it but the funny part is even with out DDR2 it is getting though more data than the one with DDR2 due to the ingetraded memory control on the CPU it self. But also remeber DDR2 is still really new. and the AMD chips are still out running the intel chips that do support along with the Apple chips because of the ingrated modal it self

Mav451
Jan 18, 2005, 06:43 PM
Anyway DDR2, as the rumor mill goes, may be skipped in its entirety for the next generation DDR standard. DDR2, until only recently, finally started reaching latencies that are even marginally close to DDR (cas 3). Cas 3, in the DDR1 world is value-ram territory, where a gig can be had for as low $100-120. Try finding a gig of DDR2 for that kind of money >> it ain't gonna happen.

Cas3 DDR2 doesn't come in until you hit the $230-250 mark. Just for cas3!

On your other point of DDR maxing out at 233, I'm afraid I'm going to have to differ. G.Skill, a Taiwanese Memory company is one of many companies using the legendary Samsung TCCD (Brainpower PCB) DDR chips that are "rated" at up to 250Mhz officially. However, G.Skill has tested their chips to hit as high as 275Mhz, and obviously overclockers reach even higher than that (e.g. 290 or 300Mhz are not uncommon).
http://www.gskill.com/pc4400-2.5-3-3-7-pc3200-tccd-2-2-2-5-dc.html

And for your viewing pleasure, a pic of an overclock by one of the GSkill employees themselves:
http://www.e04hardware.com/fx55/fx55ram9k.jpg

Yes that means DDR600 if you want marketing speak. They do tend to work much better on the 939 platform (the 754 platform can only do it with one stick, up to 240-250, as opposed to 939 where it can hit 300 easily in dual channel).

psycho bob
Jan 18, 2005, 06:45 PM
Not wanting to argue with you I just got the details off the Crucial website. The fastest non DDR2 RAM they sell is PC4000 or DDR 500. The fastest DDR2 RAM they sell is 667MHz. I quite agree that with DDR RAM you have the speed to get the true clock speed. You use the example that the fastest is DDR 566MHz but 233x2 is not that. So unless 100MHz just vanished you did your sums wrong.
Using dual channel RAM effectively doubles the bandwidth. So for DDR400 it works out as 200x 2(multiplier) = 400 x2(dual channel) =800MHz.
For single CPU Opteron systems the memory bandwidth is the same as it is for the G5 6.4Gb/s, the only question is one of latency which favours the AMD design. Only when you add more CPU's does the bandwidth increase over that of the G5. I assume ths isbecause while the G5 shares RAM between processors the Opteron has it dedicated to each CPU is dual configuration.
I still don't see how having the integrated memory controller means you can get data faster than the speed of the RAM you use. All you do is remove the latency and free up the FSB into the CPU for other tasks.

Timelessblur
Jan 18, 2005, 06:56 PM
Not wanting to argue with you I just got the details off the Crucial website. The fastest non DDR2 RAM they sell is PC4000 or DDR 500. The fastest DDR2 RAM they sell is 667MHz. I quite agree that with DDR RAM you have the speed to get the true clock speed. You use the example that the fastest is DDR 566MHz but 233x2 is not that. So unless 100MHz just vanished you did your sums wrong.
Using dual channel RAM effectively doubles the bandwidth. So for DDR400 it works out as 200x 2(multiplier) = 400 x2(dual channel) =800MHz.
For single CPU Opteron systems the memory bandwidth is the same as it is for the G5 6.4Gb/s, the only question is one of latency which favours the AMD design. Only when you add more CPU's does the bandwidth increase over that of the G5. I assume ths isbecause while the G5 shares RAM between processors the Opteron has it dedicated to each CPU is dual configuration.
I still don't see how having the integrated memory controller means you can get data faster than the speed of the RAM you use. All you do is remove the latency and free up the FSB into the CPU for other tasks.

other wise it also reduces stress off the FSB to where it can do more with the ram instead of hte CPU. Sorry dont remeber where they showed the bench marks in how the lack of DDR2 or running full DDR the AMD 64 where still faster than the Pent 4 that could run the DDR2. The intgerted control basicly makes the CPU much less relanted on the FSB to handed some stuff. But to translate to the intel numbers from what AMD runs it runs at 1.6ghz. So that should be some food for though

Mav451
Jan 18, 2005, 06:57 PM
um, RAM and FSB is all about latency. While the G5's run on 3-3-3-8 sticks of RAM, Opterons/FX's run can from anything as slow as 3-3-3-8, to something as fast as 2-2-2-5.

If you don't understand latencies, then you won't understand why AMD has an inherent memory bandwidth advantage (at least for now). If G5's could run their memory at cas 2 and Trcd (ras to cas) 2, they'd gain a substantial amt of bandwidth, but w/ the delay of communicating to a northbridge on the motherboard, the benefits of these low latencies are considerably reduced.

An Opteron/FX/A64 (939) chip can "have cake, and eat it too" cuz not only does it have the integrated memory controller, but it has the option of running cas2 and trcd 2 as well. And of course, overclocks to further enhance bandwidth.

Considering I haven't really looked into the G5 firmware, I wonder if it is even possible to change those latencies in the OS. With Windows, it is done rather easily in real-time, so I'm sure if someone develops to software, Macs can at least get cas2 and trd2.

psycho bob
Jan 18, 2005, 07:00 PM
Just read an interesting article on tomshardware.com which discusses dual channel RAM and what bandwidth differences it gives. For systems without on board memory controllers or ultra fast DDR buses like the G5 the RAM is held back by the FSB of the processor. So in the case of an Athlon XP running at 200MHz using DDR400 in dual channel configuration would only provide 3.2GB/s of bandwidth rather than the 6.4 we see on the G5 and Opteron systems.
The G5 does not have this problem its FSB can easily soak up the full throughput of dual channel DDR400 and apple could have increased the RAM spec to DDR500 and it would still have been fully utilised.

Timelessblur
Jan 18, 2005, 07:05 PM
Just read an interesting article on tomshardware.com which discusses dual channel RAM and what bandwidth differences it gives. For systems without on board memory controllers or ultra fast DDR buses like the G5 the RAM is held back by the FSB of the processor. So in the case of an Athlon XP running at 200MHz using DDR400 in dual channel configuration would only provide 3.2GB/s of bandwidth rather than the 6.4 we see on the G5 and Opteron systems.
The G5 does not have this problem its FSB can easily soak up the full throughput of dual channel DDR400 and apple could have increased the RAM spec to DDR500 and it would still have been fully utilised.


I might like to point out that the G5 computer are still only running DDR not DDR2 mind you it is running in dual channel which the opiton does since it is on socket 940. the AMD64 that run on socket 754 can not run dual channel but due to chip articature it still can out run equivlent chips. so even with the stangle hold it was still out passing P4 running in dual channel in memory test. Remeber than amd than run on socket 754 or higher have among the highest rating for memory test.

Counterfit
Jan 18, 2005, 07:07 PM
You guys gave me a headache :(

psycho bob
Jan 18, 2005, 07:18 PM
I quite agree latency is an issue, but most people will never encounter its problems. For building your low cost supercomputer or editing your Final Cut Pro video utilising the internal hard drives, FW800, RAM and both processors the latency issue becomes something of a mute point because the amount of time lost is in the milliseconds rather than the seconds/minutes. I have no doubt IBM will sort this out, probably at the same time they go dual core like the Power 5 design (that is a cracking CPU).
If I was building another PC I would do as I always have and use AMD processors. We needn't even discuss Intel at the moment with their quad pumped over heating P4, any next gen processor like the G5 or Opteron will eat it for breakfast. Only Intel's aility to ramp up the clock speed has allowed them to keep face even though it has become an over complicated inprecise beast of a chip. As it is I will stick with my G5's, for art/design they are just so much more powerful than any PC system thanks to the superior OS etc.
We all seem to have forgotten the original question :p . If we forget about memory bandwidth, CAS, latency etc etc... the fastest FSB in the industry belongs to the dual 2.5 G5 at 1.25GHz (625x2 (DDR))

psycho bob
Jan 18, 2005, 07:19 PM
You guys gave me a headache :(

I've had more painkillers today then ever before lol. I think I will withdraw quietly ;)

diamond geezer
Jan 18, 2005, 08:39 PM
I wish I could begin to understand all this talk, but despite my lack of knowledge I will add my "tuppence" worth.

G5 logic boards are described in Apple's parts database as either 167MHz for the 1.6GHz machine or 233MHz for the 1.8 & 2GHz.

The 2.5GHz does not mention speed in its parts description.

Is this any help?

daveL
Jan 18, 2005, 09:06 PM
I might like to point out that the G5 computer are still only running DDR not DDR2 mind you it is running in dual channel which the opiton does since it is on socket 940. the AMD64 that run on socket 754 can not run dual channel but due to chip articature it still can out run equivlent chips. so even with the stangle hold it was still out passing P4 running in dual channel in memory test. Remeber than amd than run on socket 754 or higher have among the highest rating for memory test.
Does it run OS X? Does it run iLife '05? No, so who gives a hoot? I know the subject of this thread is very specific, but yet again, it has degenerated into a "my HW is better than your HW". If the HW runs Windows, who cares? Junk, crap, nada. Bottom line: Does the HW/SW platform solve your problem, is it easy to use, is it secure, is it within your budget (including your time)?

Timelessblur
Jan 18, 2005, 09:53 PM
Does it run OS X? Does it run iLife '05? No, so who gives a hoot? I know the subject of this thread is very specific, but yet again, it has degenerated into a "my HW is better than your HW". If the HW runs Windows, who cares? Junk, crap, nada. Bottom line: Does the HW/SW platform solve your problem, is it easy to use, is it secure, is it within your budget (including your time)?
and yet again when people realize apple hardware is not the best they go to the famus We have OSX what about games. this is about the hardware face the facts the apple hardware is not the best out there.

psycho bob
Jan 18, 2005, 11:27 PM
and yet again when people realize apple hardware is not the best they go to the famus We have OSX what about games. this is about the hardware face the facts the apple hardware is not the best out there.

Hey come on lets look at the facts. Your saying apple hardware is not the best that is your right to do so but surely you cannot be basing that whole premise on RAM latency. At the end of the day you can use and think what ever you like, we all have our own opinions. Mine is that speed asside (that can be discussed and argued until hell freezes over) the G5 is the best desktop out there bar none. From its build, looks, ease of use and overall performance it is an unbeatable package and that is before you consider the OS and software. Try putting together a top of the line Opteron system for below 2000 (or $ equivalent). At the end of the day the Opteron is essentially a server CPU or one for very highend workstations, I personally do not see it as a competitor to the G5 if anything it goes after the IBM Power 5. The G5 is a readily accessible 64bit CPU which is far more useable and faster in it's target market then the Athlon 64FX and anything Intel can muster.
At the end of the day people couldn't really give a toss about FSB, latency etc, they just want a fast computer that is reliable and allows them to use the software they want. Most of the people I know use PC's and are pretty well up in technology matters and every single one without fail has been impressed with the G5, that doesn't mean they will buy it but they recognise it for what it is a great piece of engineering. The arguement always seems to end up with 'what about games'... well what about them? The mac has never really been a gaming machine but I've never had any trouble running the latest ones that are released and thanks to the dual processor architecture I can whack everything on full have photoshop rendering in the background and everything works great, try doing that on your single CPU machine regardless of the processor.
IBM and AMD have been working closely of late developing new technologies with relation to CPU manufacture. At the end of the day the Opteron has benefits over the G5 and vice versa, both are great chips simple as that. Which you choose depends on what you do and what system you want. But to buy something over something else based on one small aspect which in normal use isn't noticeable either means your work is very specialised or you really like boasting about your on chip memory controller ;)

psycho bob
Jan 18, 2005, 11:30 PM
I wish I could begin to understand all this talk, but despite my lack of knowledge I will add my "tuppence" worth.

G5 logic boards are described in Apple's parts database as either 167MHz for the 1.6GHz machine or 233MHz for the 1.8 & 2GHz.

The 2.5GHz does not mention speed in its parts description.

Is this any help?

Do you have a link I'd be interested in reading that information?

Timelessblur
Jan 18, 2005, 11:46 PM
Hey come on lets look at the facts. Your saying apple hardware is not the best that is your right to do so but surely you cannot be basing that whole premise on RAM latency. At the end of the day you can use and think what ever you like, we all have our own opinions. Mine is that speed asside (that can be discussed and argued until hell freezes over) the G5 is the best desktop out there bar none. From its build, looks, ease of use and overall performance it is an unbeatable package and that is before you consider the OS and software. Try putting together a top of the line Opteron system for below 2000 (or $ equivalent). At the end of the day the Opteron is essentially a server CPU or one for very highend workstations, I personally do not see it as a competitor to the G5 if anything it goes after the IBM Power 5. The G5 is a readily accessible 64bit CPU which is far more useable and faster in it's target market then the Athlon 64FX and anything Intel can muster.
At the end of the day people couldn't really give a toss about FSB, latency etc, they just want a fast computer that is reliable and allows them to use the software they want. Most of the people I know use PC's and are pretty well up in technology matters and every single one without fail has been impressed with the G5, that doesn't mean they will buy it but they recognise it for what it is a great piece of engineering. The arguement always seems to end up with 'what about games'... well what about them? The mac has never really been a gaming machine but I've never had any trouble running the latest ones that are released and thanks to the dual processor architecture I can whack everything on full have photoshop rendering in the background and everything works great, try doing that on your single CPU machine regardless of the processor.
IBM and AMD have been working closely of late developing new technologies with relation to CPU manufacture. At the end of the day the Opteron has benefits over the G5 and vice versa, both are great chips simple as that. Which you choose depends on what you do and what system you want. But to buy something over something else based on one small aspect which in normal use isn't noticeable either means your work is very specialised or you really like boasting about your on chip memory controller ;)


fine you want to play that game your right that the opteron is a server chip but the AMD 64 line is a normal computer chip that is still out running the G5

For software not going ot using games and besidce the fact I like plently of games the mac does not have. Besides that I have over 1k software that I use that is not games that oh yeah the OSX does not have. I am also planing on adding autocad to my desktop with in the next year or so and oh yeah macs sucks when it comes to cad work. This program are profection level aps so utter lack of software is a vaild reason.
Depending on what I am doing depends if I noticed the extra power some stuff it is very noticble some stuff the computer is overkill.
For the mess I put up with the OS no dont really put much time in it and I know my computer is clean I know how to take care of a computer . For most stuff most argument that Mac users give I can tell you guys over blow it.
I could start poking holes in the Imac and point out I paid less and my computer is more powerful. I wanted to stay out of that.

solvs
Jan 18, 2005, 11:52 PM
I wish I could begin to understand all this talk, but despite my lack of knowledge I will add my "tuppence" worth.

G5 logic boards are described in Apple's parts database as either 167MHz for the 1.6GHz machine or 233MHz for the 1.8 & 2GHz.

The 2.5GHz does not mention speed in its parts description.

Is this any help?
Um... what? Ok, the old 1.6 used to use 333MHz DDR RAM (which runs at 167MHz rising and falling, DDR = double data rate). But it required you to run 2 of the same sticks together for a dual channel rate of 666MHz, but it still had an 800MHz FSB. The current iMacs have a slower FSB on their G5s, but the 2.5GHz G5 is running a 1.25GHz FSB, half the speed of the CPU.

This whole argument is still silly though. Even with DDR2 (which has a higher latency BTW, so it can be slower at times even), or overclocked DDR RAM running at over 400MHz, there are a ton of other factors that effect overall speed.

To answer the original question, the highest rated G5 (at 2.5GHz) has a FSB of half the CPU speed... 1.25GHz. The RAM is 400MHz DDR (rising and falling 200MHz) running in dual channel, for an effective speed of 800MHz. Whether it's faster than other chips is debatable. For some things it is, for others it isn't. Sorry, but it's funny we're still talking about it.

I need to get back to work. :p

brap
Jan 19, 2005, 12:09 AM
...(snip)...
I could start poking holes in the Imac and point out I paid less and my computer is more powerful. I wanted to stay out of that.Horses for courses.

You want your Windows PC? Fine, it's cool, good luck, hope the CAD apps work well for ya.

The fact is Macs are simpler, package-for-package. Not everybody can build a PC themselves, very few people can look after the Windows OS properly. The hardware too, x86 develoment has so much more R&D pushed into it it's no wonder it moves on quicker. If you think about the scale of the thing, isn't it remarkable that Apple is still in business, let alone pushing out feasible, powerful, affordable Mac minis, and Superclusters of G5s? You don't seem to be "Getting" this argument - which is fine, since the thread title is all about that. Just perhaps be aware some people will argue this case.

My real question is - how does it feel to be crusading against the poor, uneducated Mac-users? "Zealots", if you will?

psycho bob
Jan 19, 2005, 12:16 AM
fine you want to play that game your right that the opteron is a server chip but the AMD 64 line is a normal computer chip that is still out running the G5

For software not going ot using games and besidce the fact I like plently of games the mac does not have. Besides that I have over 1k software that I use that is not games that oh yeah the OSX does not have. I am also planing on adding autocad to my desktop with in the next year or so and oh yeah macs sucks when it comes to cad work. This program are profection level aps so utter lack of software is a vaild reason.
Depending on what I am doing depends if I noticed the extra power some stuff it is very noticble some stuff the computer is overkill.
For the mess I put up with the OS no dont really put much time in it and I know my computer is clean I know how to take care of a computer . For most stuff most argument that Mac users give I can tell you guys over blow it.
I could start poking holes in the Imac and point out I paid less and my computer is more powerful. I wanted to stay out of that.

Try and pick up an earlier version of Autocad around 2000 or the version before. It seems to get more and more bloated with every release, 2000 was good once they ironed out the bugs of the initial launch product. I have a PC and it chugs along fine never had any issues with it other than a failed hard drive. Like I said you use what best fits the work you do.
I have no problems with PC's at all but for the design and photography I do would I swap my G5 for an Athlon or Opteron based system... no, that is my choice. Having invested in Apple's Pro Apps (annoyingly before they released the production suite), Quark Xpress, Adobe Creative Suite, Macromedia Studio etc it would be foolish to jump platforms and I've had no reason to even give it thought. I've used macs since the LC days and will continue to use them. The Athlon 64 is a very good chip and beats the P4 and G5 in some benchmarks just as they beat it in others. I couldn't really care less.
I assume you are a PC user first and foremost? Why does it matter to you what we think, at no point in this entire thread have I or anyone else stated the G5 is the best processor. All we wanted to clarify that the fastest FSB currently available belongs to the G5. Will it always be like that? Probably not. And as people have pointed out there are so many other things that go to creating a fast, but above everything, reliable compter.

Timelessblur
Jan 19, 2005, 01:13 AM
Try and pick up an earlier version of Autocad around 2000 or the version before. It seems to get more and more bloated with every release, 2000 was good once they ironed out the bugs of the initial launch product. I have a PC and it chugs along fine never had any issues with it other than a failed hard drive. Like I said you use what best fits the work you do.
I have no problems with PC's at all but for the design and photography I do would I swap my G5 for an Athlon or Opteron based system... no, that is my choice. Having invested in Apple's Pro Apps (annoyingly before they released the production suite), Quark Xpress, Adobe Creative Suite, Macromedia Studio etc it would be foolish to jump platforms and I've had no reason to even give it thought. I've used macs since the LC days and will continue to use them. The Athlon 64 is a very good chip and beats the P4 and G5 in some benchmarks just as they beat it in others. I couldn't really care less.
I assume you are a PC user first and foremost? Why does it matter to you what we think, at no point in this entire thread have I or anyone else stated the G5 is the best processor. All we wanted to clarify that the fastest FSB currently available belongs to the G5. Will it always be like that? Probably not. And as people have pointed out there are so many other things that go to creating a fast, but above everything, reliable compter.

simple it is one thing to have an opinan it is another to basicly start saying blantly lies. When clearly most mac users dont know what htey are talking about. I rather people have correct facts instead of the famus apple BS and users who complain and refuse to see any good in PCs and MS windows

Bigheadache
Jan 19, 2005, 01:24 AM
All we wanted to clarify that the fastest FSB currently available belongs to the G5. Will it always be like that? Probably not. And as people have pointed out there are so many other things that go to creating a fast, but above everything, reliable compter.

Well congrats to the marketing types at Apple, Intel, and AMD for making a complete meal out of this.

Anyway, to get back on topic, a FSB is traditionally the connection from the memory controller to the CPU. In an AMD AThlonXP, G5, and an Intel, the memory controller is in the northbridge chip which means the FSB also doubles up as part of the system bus.

On an AMD64 it is different as the memory controller is internal to the CPU die. Therefore, the FSB must be the fastest of all chips because as an internal on chip component it operates at the CPU's native speed. The Hypertransport link on an AMD64 is the system bus, not the FSB.

So in answer to the OP's question, your professor is correct. The fastest FSB on a G5 is 1.25GHz but the fastest AMD64 FSB available is 2.6GHz (the FX55).

Aside from the integrated memory controller and 64bit extensions (which aren't used on Windows), the A64 is mainly an enhancement of the AthlonXP. Given that, we can surmise that its the integrated memory controller which is the main reason for its excellent performance vis a vis the AthlonXp, so I for one hope that an integrated memory controller appears somewhere on the PowerPC roadmap.

psycho bob
Jan 19, 2005, 03:03 AM
I think the 1MB of L2 cache helps somewhat as well.
What I do find intriguing though is the confusion within the industry itself. A PC site that I trust and is very expansive www.tomshardware.com have detailed reviews of all the athlon products including the new FX55. They never state the FSB. Where reference can be found for the FX series it is stated as being 400MHz (after multiplier) http://www.amdboard.com/athlon_64_fx-55.html http://www.amdreview.com/reviews.php?rev=fx-55-4000
On a personal level (I'm not an IT expert) I don't understand how having the connection between CPU and RAM running at processor speed can be of such a great benefit when the finite speed of the DDR400 in dual channel configuration is 800MHz. I understand the latency issues and how more than with an other CPU having low latency DIMMs help but it can't get there any quicker than the clock speed the memory operates at.
One issue with having the memory controller built in is the fact you ae forced to use specific RAM. A motherboard maker cannot simply design the board to use DDR2 for example the CPU has to support it. I beleive when the FX was originally introduced is supported 266/333 and now adds 400 to the mix. If they want to add DDR2 or faster they have to redesign the whole die.
I need more pain killers :o

Mav451
Jan 19, 2005, 09:36 AM
psycho bob: Regurgitating what you read on the Internet doesn't show that you've learned anything. Second, for the love of god, do NOT go to TomsHardware to "learn about AMD". Tom's was notorious for skewing their benchmarks toward Intel. If you want to learn about AMD chips, go to reputable sites like The Tech Report, [H]ardOCP, Anandtech, or Xbit Labs.

You also keep talking about how latencies don't mean jack--until you actually see the difference first hand, you will never understand its significance. Why don't you go find someone with an A64, and have them show you the difference between 3-3-3-8 RAM and 2-2-2-5. Trd2 and cas2 equates to literally a 10-12Mhz increase in memory FSB (e.g I get the same memory bandwidth at 200Mhz with those latencies as I would get at 210-212 with the much looser settings). While memory bandwidth's impact is most significant in gaming, other applications like Divx/MPEG encoding could use it>> it means shaving off seconds, to minutes, to hours even. In PShop it could mean waiting 10-12 less seconds on applying a filter.

Regarding your misunderstanding of FSB, yes, while certain sites would claim that the FX-55 or the FX-series is running at 400Mhz (which means 400 * 8 = 3.2GB/s of memory bandwidth), that couldn't be farther from the truth.
http://www.hardocp.com/article.html?art=Njc1LDI=

B/c of having not only a dual-channel memory controller, but an integrated one, it achieves nearly 6GB/s of memory bandwidth. Running at "only 400Mhz", it far exceed Intel's offering on the 3.46EE, which has an "FSB" of 1066Mhz. Not on the other hand, when I run at "only 400Mhz" or 430Mhz to be exact, my results are much different than what an FX would get. B/c the Bartons do not have an IMC, Bartons are already inherently capped in memory performance and also in CPU performance. What some people forget is that the newer K8 core (Opteron/FX/Athlon64) chips are still essentially a modification and improvement of the Barton (K7) core. Reduced latencies have meant improving anywhere from 50% to 200% of the performance a Barton would have at the same clockspeed. I can tell you that if I had an IMC with my Barton, @ 2.55GHz, it would be in the range of singlehandedly equalling or exceeding dualG5 systems. However, the reality is that w/o that IMC, my Barton is closer to a single G5 (1.8-2.0) range.

wrldwzrd89
Jan 19, 2005, 02:24 PM
psycho bob: Regurgitating what you read on the Internet doesn't show that you've learned anything. Second, for the love of god, do NOT go to TomsHardware to "learn about AMD". Tom's was notorious for skewing their benchmarks toward Intel. If you want to learn about AMD chips, go to reputable sites like The Tech Report, [H]ardOCP, Anandtech, or Xbit Labs.

You also keep talking about how latencies don't mean jack--until you actually see the difference first hand, you will never understand its significance. Why don't you go find someone with an A64, and have them show you the difference between 3-3-3-8 RAM and 2-2-2-5. Trd2 and cas2 equates to literally a 10-12Mhz increase in memory FSB (e.g I get the same memory bandwidth at 200Mhz with those latencies as I would get at 210-212 with the much looser settings). While memory bandwidth's impact is most significant in gaming, other applications like Divx/MPEG encoding could use it>> it means shaving off seconds, to minutes, to hours even. In PShop it could mean waiting 10-12 less seconds on applying a filter.

Regarding your misunderstanding of FSB, yes, while certain sites would claim that the FX-55 or the FX-series is running at 400Mhz (which means 400 * 8 = 3.2GB/s of memory bandwidth), that couldn't be farther from the truth.
http://www.hardocp.com/article.html?art=Njc1LDI=

B/c of having not only a dual-channel memory controller, but an integrated one, it achieves nearly 6GB/s of memory bandwidth. Running at "only 400Mhz", it far exceed Intel's offering on the 3.46EE, which has an "FSB" of 1066Mhz. Not on the other hand, when I run at "only 400Mhz" or 430Mhz to be exact, my results are much different than what an FX would get. B/c the Bartons do not have an IMC, Bartons are already inherently capped in memory performance and also in CPU performance. What some people forget is that the newer K8 core (Opteron/FX/Athlon64) chips are still essentially a modification and improvement of the Barton (K7) core. Reduced latencies have meant improving anywhere from 50% to 200% of the performance a Barton would have at the same clockspeed. I can tell you that if I had an IMC with my Barton, @ 2.55GHz, it would be in the range of singlehandedly equalling or exceeding dualG5 systems. However, the reality is that w/o that IMC, my Barton is closer to a single G5 (1.8-2.0) range.
Your post shows that Apple could learn some things from AMD about how to design their computers. How much of it could be applied to the G5 design is debatable. It seems that many, if not all, of the improvements Apple could make based on knowledge of AMD's design revolve around memory - is this correct?

ajkst1
Jan 19, 2005, 02:28 PM
So basically this thread crumbled into a "My FSB is better than your FSB."

What is the fastest FSB? Is it the 1.25 Ghz on the 2.5 Ghz G5 or something from AMD? Am I right or is my prof right?

psycho bob
Jan 19, 2005, 03:10 PM
If I'm wrong I don't mind I'm not trying to be clever just to learn. At no point did I say that latency wasn't important. What I did say was that unless you compared two systems side by side doing very repetitive tasks the difference wouldn't be noticeable to the average user. The article you linked says basically that.
What I asked but still haven't found an answer to is how using dual channel channel DDR400 RAM giving you effectively 800MHz can be made any quicker on the athlons processor speed FSB compared to the G5's 1.25GHz FSB. The latency as I understand is not only in the RAM but also the path it has to take to the CPU, this is where the FX has the advantage. The system controller on the G5 doesn't operate like older North Bridge designs and operates a point to point architecture with all main subsystems having direct access to the RAM. As the FX is linked directly to the RAM does that mean all memory access has to be diverted via the CPU?
Both the AMD K8 cores and the G5 have memory bandwidth of 6.4GB/s as they essentially operate in the same way the only difference being the route the data takes. So are we saying that the only real difference between the G5 and K8 is the reduced latency of the latter?
In which case the question becomes what real world advantages does the reduced latency have? You say it equates to around 12MHz would the difference then not be made mute if apple simply used faster DDR memory than the AMD systems?
So before you blow my head off and criticise everything I've said just let me reiterate I'm just trying to understand this myself. I'm not sticking up for apple or IBM. Any info you can provide is most welcome :)

psycho bob
Jan 19, 2005, 03:13 PM
So basically this thread crumbled into a "My FSB is better than your FSB."

What is the fastest FSB? Is it the 1.25 Ghz on the 2.5 Ghz G5 or something from AMD? Am I right or is my prof right?

It would appear your prof at least on paper. What I'm trying to find out is what real world difference the super fast FSB for RAM on the AMD chip has when the DDR400 memory is so much slower.

diamond geezer
Jan 19, 2005, 03:18 PM
Do you have a link I'd be interested in reading that information?

There is no information to read, it's just a part name.

I can't send you the link, it's for Apple Techs only.

simie
Jan 19, 2005, 04:50 PM
http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_9485_9488^9564~74984,00.html

You folk might want to read this.

:cool:

psycho bob
Jan 19, 2005, 05:11 PM
http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_9485_9488^9564~74984,00.html

You folk might want to read this.

:cool:

The architecture data and comment was interesting. Do you have a link for the Athlon FX white paper? Hopefully that will go into greater detail about the specific benefits and perhaps put some figures to the words. I'll have a lok for it myself if I get a chance.

Bigheadache
Jan 19, 2005, 07:22 PM
The architecture data and comment was interesting. Do you have a link for the Athlon FX white paper? Hopefully that will go into greater detail about the specific benefits and perhaps put some figures to the words. I'll have a lok for it myself if I get a chance.

When you talk about the 6.4gb/s bandwidth, you are actually talking about a purely theoretical capability. If you go to PC forums and see what memory scores people are getting using SANDRA or any other diagnostic tool, its not unusual for socket 939 A64 owners with dual channel DDR400 to get 6000mb/s. But on Intel systems with the same memory people are only getting 4500-5000mb/s when theoretically both should be getting 6.4gb/s. The theoretical FSB bandwidth of an Intel 1066FSB chip is actually something like 8.4gb/s.

With scores like that, its obvious that AMD don't see a compelling need to move to DDR2. Sure its a disadvantage that to provide DDR2 support the chip has to be redesigned, but AMD excels because of the efficiency of its integrated memory controller not by ramping up memory speeds. As I said previously, I hope this is something which is considered for the G5 at some stage.

As for latencies, they aren't important on a Intel chip, and very important on an AthlonXP. However, on an A64 they aren't really important as long as you can get 1T command rate. if you are stuck with 2T then its costing you about 20-30MHz in RAM speed. CAS timing does not have a major impact.

simie
Jan 20, 2005, 01:19 AM
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/31366.pdf

This is the only white paper regarding the 64FX that I could find.

:cool:

psycho bob
Jan 20, 2005, 08:09 PM
If you don't understand latencies, then you won't understand why AMD has an inherent memory bandwidth advantage (at least for now). If G5's could run their memory at cas 2 and Trcd (ras to cas) 2, they'd gain a substantial amt of bandwidth, but w/ the delay of communicating to a northbridge on the motherboard, the benefits of these low latencies are considerably reduced.

Considering I haven't really looked into the G5 firmware, I wonder if it is even possible to change those latencies in the OS. With Windows, it is done rather easily in real-time, so I'm sure if someone develops to software, Macs can at least get cas2 and trd2.

While looking through an Apple developer doc for something else I came across the CAS compatibility chart for the G5.
The officially supported lantencies are; 2, 2.5, 3, 4 and 5. No need to go fiddling with firmware just put the RAM in.

Mav451
Jan 20, 2005, 09:50 PM
Just b/c its supported doesn't mean it will run at that speed. How do you know if the G5 will default to JEDEC 3200 spec cas3 for stability's sake? On alot of PC motherboards, even if they are capable of 2-2-2-5 latencies, they won't initially run at that until you go into BIOS to set it.

If someone has a friend with Corsair XL or G.Skill RAM in their computer, ask them if you can borrow it and put in in your G5. If it does run at 2-2-2-5 w/o user intervention, I'll be pretty impressed, but I won't be shocked if it defaults to 2-3-3-6, or the standard 3-3-3-8.

solvs
Jan 21, 2005, 12:09 AM
So basically this thread crumbled into a "My FSB is better than your FSB."

What is the fastest FSB? Is it the 1.25 Ghz on the 2.5 Ghz G5 or something from AMD? Am I right or is my prof right?
There is no easy answer. The G5 is 1.25. Not Apple's marketing, that's what it is. The AMD is 2.6, but it's also 800. I'd just let it go.

psycho bob
Jan 21, 2005, 02:46 AM
Just b/c its supported doesn't mean it will run at that speed. How do you know if the G5 will default to JEDEC 3200 spec cas3 for stability's sake? On alot of PC motherboards, even if they are capable of 2-2-2-5 latencies, they won't initially run at that until you go into BIOS to set it.

If someone has a friend with Corsair XL or G.Skill RAM in their computer, ask them if you can borrow it and put in in your G5. If it does run at 2-2-2-5 w/o user intervention, I'll be pretty impressed, but I won't be shocked if it defaults to 2-3-3-6, or the standard 3-3-3-8.

Do you have a tool that would measure RAM latency on the mac? I'd be interestd in finding out but have got a clue hoe it could be measured without third party software.

ddtlm
Jan 21, 2005, 03:41 AM
psycho bob:

Both the AMD K8 cores and the G5 have memory bandwidth of 6.4GB/s as they essentially operate in the same way the only difference being the route the data takes. So are we saying that the only real difference between the G5 and K8 is the reduced latency of the latter?
Yes. Often enough, all that matters is how fast you get your data from RAM.

ajkst1:

What is the fastest FSB? Is it the 1.25 Ghz on the 2.5 Ghz G5 or something from AMD? Am I right or is my prof right?
AMD wins easily. (Though in both cases the FSB has more bandwidth than the system RAM, AMD has a much lower latency, which is very important.)

Bigheadache:

I for one hope that an integrated memory controller appears somewhere on the PowerPC roadmap.
Moto is on it, the MPC8641, based on the G4. Should uncork some performance, depending on the task, but who knows if Apple will use it. Note 1MB L2, dual channel DDR2, PCI-express support, not bad at all.

http://www.freescale.com/webapp/sps/site/overview.jsp?code=DRPPCDUALCORE

They even had a nice PDF:

http://www.freescale.com/files/32bit/doc/fact_sheet/MPC8641DFACT.pdf

edit: Hey, the 8641 even has four integrated gigabit ethernet controllers. :) Someone could make such a sweet minimac wrapped around a 8641D (the dual core version).

wrldwzrd89
Jan 21, 2005, 04:39 AM
Just b/c its supported doesn't mean it will run at that speed. How do you know if the G5 will default to JEDEC 3200 spec cas3 for stability's sake? On alot of PC motherboards, even if they are capable of 2-2-2-5 latencies, they won't initially run at that until you go into BIOS to set it.

If someone has a friend with Corsair XL or G.Skill RAM in their computer, ask them if you can borrow it and put in in your G5. If it does run at 2-2-2-5 w/o user intervention, I'll be pretty impressed, but I won't be shocked if it defaults to 2-3-3-6, or the standard 3-3-3-8.
I remember reading somewhere (maybe it was on these forums?) that what the G5 actually does is slow the memory down. The G5 can reduce the memory's speed as much as it wants to - even down to 100 MHz (DDR50) or lower, if that's what's needed before the G5 likes the memory speed. It won't do this if you're using standard 3-3-3-8 RAM though.

psycho bob
Jan 21, 2005, 04:48 AM
I remember reading somewhere (maybe it was on these forums?) that what the G5 actually does is slow the memory down. The G5 can reduce the memory's speed as much as it wants to - even down to 100 MHz (DDR50) or lower, if that's what's needed before the G5 likes the memory speed. It won't do this if you're using standard 3-3-3-8 RAM though.

Never heard of this. The G5 will slow faster DDR modules down to the machines spec, so fitting DDR500 would be slowed to 400. The G5 does have the ability to slew the sytem bus (If I remember correctly, it can certainly slew the CPU speed) depending upon usuage.

wrldwzrd89
Jan 21, 2005, 04:54 AM
Never heard of this. The G5 will slow faster DDR modules down to the machines spec, so fitting DDR500 would be slowed to 400. The G5 does have the ability to slew the sytem bus (If I remember correctly, it can certainly slew the CPU speed) depending upon usuage.
I'm not terribly surprised that you haven't heard about this - I have to get ready to go to work, so I don't have time to hunt down a link right now. Maybe I'll get around to it later (when my iLife '05/iWork order FINALLY ships :) )