Motorola MPC7457 Summary

[MacRumors]

Architosh (http://www.architosh.com/news/2002-10/2002c-1023-mcp7457-rm1.phtml) posts some details and speculation on Motorola's upcoming processors. Much of the information from this report as well as the afore mentioned German report appears to be have originated from a PDF (http://e-www.motorola.com/collateral/SNDF2002RECAP_Q1228.pdf) (pulled) that was posted on Motorola's site. That particular document has since been pulled.

The essense is caputured by Architosh in this summary:


It appears from this road map that the next Motorola "G-something" processor will be a G4, its model number being MPC7457, with a MHz range between 867-1833MHz. This chip is based on a SOI (silicon on insulator), .13micron process and appears planned for sometime in 2003. The MPC7457-RM chip, planned for 2004 is more mysterious and includes RapidIO.

The article also attempts to pull together older rumors, and provides some unrealistic predictions of upcoming PowerMac releases.

Reference to the PDF was previously made in this thread (http://forums.macrumors.com/showthread.php?threadid=13126) with a screenshot of the since removed PDF.

[gandalf55]

man - what the hell... information being pulled makes me think it's accurate. and now i think that moto officially has their lips tightly around the suck pipe. moore's law is going to skip apple i guess.

[reyesmac]

I am thinking we might not see a processor go above the 2 gig mark if it even reaches that. Does the IBM chip use Rapid IO? If it does, at least that will be a great thing to have.

[rice_web]

It's very possible that we'll see this chip used in new PowerMacs, which would likely be released on or around MWSF. 1.5GHz on a new 130nm manufacturing process would yield fun overclocking possibilities.

[Scab Cake]

Is it me or is the Mhz myth getting kinda depressing with this news? I know the G4 is an incredible chip that's really fast and efficient, but I feel like I'm riding on a dying horse. I was hoping that these companies were planning for chips of at least 2 Ghz for the end of 2003. Sometimes I wish they would at least lie about the future specs...oh wait.

[reyesmac]

Originally posted by Scab Cake
Is it me or is the Mhz myth getting kinda depressing with this news?

You're problem is that you are comparing the G4 to its competition. I did that once and was told to stop whining. What you need to do is just believe Apples hype and understand that since the G4 is not running on a PC motherboard, it can be any speed Apple wants it to be and still keep up with everything out there and is worth any premium they slap on it.

[scem0]

Oh but it is such a good motherboard......

:D

[copperpipe]

your problem is that you're fixated on an overly simple solution, for your overly simple mind, which makes you a great target for advertising. Sheep, my friend, is what you become when you buy a product based on too simple an evaluation. You see, then the manufacturers can EXLPOIT your limited knowledge. Have you ever heard the saying "a little knowledge is a dangerous thing"? Well, that's you buddy ol' pal. When purchasing a computer, or any product for that matter, the bottom line is QUALITY vs. PRICE. You see now that word QUALITY is not easy to put down into one thing. I know, I know, it gives you a headache to actually have to think sometimes, but trust me, learn this lesson and the QUALITY of your life will increase. So when it comes to comparing Apples to Dells, don't think "Megahertz=What the advertising keeps telling me to focus on=duh, that's what i'll do then, duh", think "I will live with this and spend much of my time on it, so I should truly enjoy the OS, it should be as fast as I can afford, it should be constructed well (or superbly in the case of Apple), and last but not least it should come from a company that I respect, and respects me as a consumer. That should help you get started my friend. Good luck!

[GetSome681]

I'm extremely anxious to see what powermacs apple releases next. I've always been a mac fanatic, ever since my first mac (first computer) the apple IIgs. Anyways, while in college, I build a quick, quick PC...just b/c there were so many programs I needed to use, that just weren't written or available for the mac (industry specific progs). I'm out now, but I decided to redo my PC. I understand the value and quality of the Mac OS...but the PC that I built for $500 (only additional parts or things I was changing...I'd say total total would be closer to $800-900) comes extremely close to rivaling the value and quality of my mac. I don't want to turn this into a PC vs. Mac fight, b/c in my opinion, each has it's strong points...but seriously...PCs can be built cheap...but not cheap in the sense of quality of build, etc. Sure Winblows sucks...but it's hard to deny the speed of this machine...mainly it's hardware. Lots of people out there like to think that Apple is just on top of the world when it comes to making motherboards, etc. as they always trash the PC world on these topics. In reality, it comes close to the opposite.

I don't know what my point of this is...but I do know that when I compare my PC hardware to that of my Mac (or new macs even)...it's getting depressing. Sure my PC isn't as cool looking as the PMacs or any mac really...and sure Winblows blows...but honestly...I do get things done on it, and the hardware options out there are incredible. I really hope that Apple doesn't lose itself in the next year or so. I know Apple's not to blame (Moto is) as they don't produce the chips...and I'm not saying they should go x86 either...all I do know is that lately I find myself often wishing that I could run OS X on my PC.


Come on Moto...come on IBM...let's get some killer chips out!

[dojothemouse]

If I'm reading this right, motorola wants us to keep using maxbus for at least the next year and a half.

Unless they give us a 128MB L3 cache, I don't wouldn't care if they *did* match x86 speeds. All you mHz myth weenies keep dissing the x86 for performance on pipeline flushes. Well, look at our performance on a cache miss. Jesus. Might as well send for the data via postal mail rather than maxbus.

[GetSome681]

Originally posted by dojothemouse
If I'm reading this right, motorola wants us to keep using maxbus for at least the next year and a half.

Unless they give us a 128MB L3 cache, I don't wouldn't care if they *did* match x86 speeds. All you mHz myth weenies keep dissing the x86 for performance on pipeline flushes. Well, look at our performance on a cache miss. Jesus. Might as well send for the data via postal mail rather than maxbus.


True...wasn't there some test results out that said the 1.25's didn't really outdo the 1 ghz's by too much...indicating that the bus might just not be enough for the chip..?? Maybe it was an old test, but that's sorta what I remember. So...that doesn't bode too well for a 1.8 ghz chip being worth very much in practical terms.

[reyesmac]

Why does Apple even NEED a fast CPU? Why cant they just include custom video hardware that lets you do real-time video effects like the high-end video import cards have? Or why don't they include something that makes 3D super fast? Or why not just use THE BEST video card on ALL mac models? That way, the processor can be slow, but video and 3D will be fast on all Macs? Thats pretty much all that needs to be fast, well, that and the Finder, but that would be sped up by the custom video hardware.
If they had something like that they could claim to be faster than the fastest pentium on all the important stuff. Who cares if i wont be able to rip a CD at 40x speed when I could play Quake on one monitor with crazy frame rates and watch a DVD on the other monitor with no skipping. The "Myth" wouldnt matter then.
If you say that would add cost to the Mac, who cares, you know they would make it more expensive if they could and even if they do it would still be worth it for real time video/3d/finder.

[MOM]

Originally posted by GetSome681



True...wasn't there some test results out that said the 1.25's didn't really outdo the 1 ghz's by too much...indicating that the bus might just not be enough for the chip..?? Maybe it was an old test, but that's sorta what I remember. So...that doesn't bode too well for a 1.8 ghz chip being worth very much in practical terms.


The reviews I saw suggested that the 1.25's were about 25% faster than the 1.0 chips, as expected. Its just that the new and the old 1.0 machines ran about the same. Thus, all the new DDR etc doesn't seem to result in much real world advantages (but the price for 1.0 G4s sure went down). MOM

[scem0]

I understand the value and quality of the Mac OS...but the PC that I built for $500 (only additional parts or things I was changing...I'd say total total would be closer to $800-900) comes extremely close to rivaling the value and quality of my mac. I don't want to turn this into a PC vs. Mac fight, b/c in my opinion, each has it's strong points...but seriously...PCs can be built cheap...but not cheap in the sense of quality of build, etc. Sure Winblows sucks...but it's hard to deny the speed of this machine...mainly it's hardware. Lots of people out there like to think that Apple is just on top of the world when it comes to making motherboards, etc. as they always trash the PC world on these topics. In reality, it comes close to the opposite.

I don't know what my point of this is...but I do know that when I compare my PC hardware to that of my Mac (or new macs even)...it's getting depressing. Sure my PC isn't as cool looking as the PMacs or any mac really...and sure Winblows blows...but honestly...I do get things done on it, and the hardware options out there are incredible. I really hope that Apple doesn't lose itself in the next year or so. I know Apple's not to blame (Moto is) as they don't produce the chips...and I'm not saying they should go x86 either...all I do know is that lately I find myself often wishing that I could run OS X on my PC.

You totally captured what I have been trying to say back in the IBM 970 details thread. What you say is exactly how I feel. I just bought a PC that I am going to be 10x happier on then a mac I would purchase for the same money ($600), and I still think macs are better, but you can get a very fast PC for a very good price. No can do with a mac. Sorry, try to ignore this post everyone, I just had to comment on it. And I don't want to change this into a Mac vs PC argument like on the IBM 970 details thread. If you want to argue PM me. :)

[MisterMe]

Originally posted by GetSome681
I'm extremely anxious to see what powermacs apple releases next. I've always been a mac fanatic, ever since my first mac (first computer) the apple IIgs.
The Apple IIgs was an Apple II, not a Macintosh. The two lines were based on different processors and different operating systems, although System 6 did incorporate features from the Macintosh System 6.
Originally posted by GetSome681
...PCs can be built cheap...but not cheap in the sense of quality of build, etc. ....
You clearly have a different standard for quality of build than do I. The only Wintel manufacturer of note to even rival Apple in quality of build is IBM. Dell, HP/Compaq, Gateway? Forget about it.
Originally posted by GetSome681
Sure my PC isn't as cool looking as the PMacs or any mac really...
Is that the only thing you can see as the Mac advantage?
Originally posted by GetSome681
and sure Winblows blows...but honestly...I do get things done on it, and the hardware options out there are incredible. I really hope that Apple doesn't lose itself in the next year or so. I know Apple's not to blame (Moto is) as they don't produce the chips...and I'm not saying they should go x86 either...all I do know is that lately I find myself often wishing that I could run OS X on my PC.


Come on Moto...come on IBM...let's get some killer chips out! What you need to do is to stop the p*ssing contests with your Windows weenie friends. The microprocessor is just one part (or two parts in the case of duals) of a much more complicated system that is the computer. By fixating on the processor, you show a virtual total lack of understanding of what it takes to turn all of those parts into a harmonious whole.

[GetSome681]

Originally posted by MisterMe

The Apple IIgs was an Apple II, not a Macintosh. The two lines were based on different processors and different operating systems, although System 6 did incorporate features from the Macintosh System 6.

Well I apologize that I didn't know this, and that I was only 8-10 at the time...forget.

You clearly have a different standard for quality of build than do I. The only Wintel manufacturer of note to even rival Apple in quality of build is IBM. Dell, HP/Compaq, Gateway? Forget about it.

It's on some of these things that I wonder if other people have actually ever gone out and actually looked at PCs. Sure, most OTC (over-the-counter) PCs such as the Dells and the Gateways are definitely crap, however I was more referring to the average PC builder. The stereotypical PC builder has a case that's open, wires just everywhere, everything's a mess, things are falling apart, or coming loose...you know what I'm trying to say. It's most people's vision that the PC builder's computer is quite cheap, yet this isn't always the case. There are MANY cases, cables, setups, etc. out there that can yield a PC which rivals the build quality and neatness of setup (not coolness, rather organization of wires, hard drives, etc.) of the current Macs. You missed my point though...I was trying to say that they "rival" the macs...IMO Apple still has a lock-down on this category. Would I rather have my "computer components" in a PC case or an El Capitan...well besides the lack of optical drive space (MDD fixes that sorta)...it would be El Capitan all the way.

Is that the only thing you can see as the Mac advantage?

No, this goes along with the above...in terms of the overall effectiveness of the case. If you read my message...how many times do I say I love OS X...?? I guess my loving it isn't enough for it to be an advantage of the Mac..???


What you need to do is to stop the p*ssing contests with your Windows weenie friends. The microprocessor is just one part (or two parts in the case of duals) of a much more complicated system that is the computer. By fixating on the processor, you show a virtual total lack of understanding of what it takes to turn all of those parts into a harmonious whole.

I tried to make this obvious, but I guess I didn't really succeed. I'm not a Windows weenie, and honestly only have one of them, who I only use for info when I can't get things working on this h*llish of an operating system called WinXP...where things just sometimes aren't very intuititive. I do realize there are more benefits of a system than just it's cpu. Are you going to tell me though that the current Apple mobos are some great, great technological wonder that blow away the latest offerings from let's say ASUS? The fact that I have serial ata connections on my motherboard, firewire, onboard raid, needless to mention USB2, which I have no real use for at the present. Sure I can't get a serial ata drive yet, but it's nice to have those connections for when they're out soon, as it's specs have obviously been finalized, so heck...Apple should be able to put them on theirs as well, but they're not there. So what other parts are there....hmm...let's look at the ide channels. ATA100 on the new macs...wow, that's about great, running a two drive 0 raid on that with the newest SE drives can come close to saturating that...if not saturate it at times. Needless to mention you'd be hardpressed to find a PC without ATA133.

What about the ability to configure your system? What about memory settings? Can you change the aggressiveness of your memory system and its latency on the mac? Obviously that's another issue besides the cpu as well.

I could go on forever, but won't...b/c as I said..I'm not here to trash the mac, never have been, never will be. I'm just saying that I hope that Moto or IBM has some real light to bring to the platform soon. Obviously not all the fault lies with Apple, yet some does. They could have and still have a super great computer just waiting for us, yet with no powerpc cpu worthy enough for it just yet. Hopefully this won't be the situation in 2003. Enough of the PC flamewar...like I said...each has it's advantages. I also didn't annouce a winner in my opinion, so please don't try and flame my way.

[kenohki]

Originally posted by GetSome681

What about the ability to configure your system? What about memory settings? Can you change the aggressiveness of your memory system and its latency on the mac? Obviously that's another issue besides the cpu as well.


WTF? "Agressiveness of your memory system and it's latency"? You can't adjust that. First off, latency of memory is not adjustable. It just depends on what you buy, whether it's DRAM, SDRAM, MoSys 1T-SRAM or whatever. Memory latency is determined by the materials and build of the actual memory. And I'm not sure what you're talking about by "agressiveness" but I'm assuming it's something to do with paging but could you expand a little on this?

[GPTurismo]

Big Blue here we come.

Yes the PPC970 has Rapid I/O.

^_^

[ibjoshua]

Originally posted by GetSome681
...how many times do I say I love OS X...??
ummmmmm.... not once.

some people on these forums just don't get it do they?

we wouldn't be reading these fourms and devoting our valuable time to answering inane statements if we were interested in PCs. we're here because we love macs. the PC/mac comparisons, whatever their value, are wasted on the majority of us.

i_b_joshua

[locovaca]

Originally posted by MisterMe

Is that the only thing you can see as the Mac advantage?
What you need to do is to stop the p*ssing contests with your Windows weenie friends. The microprocessor is just one part (or two parts in the case of duals) of a much more complicated system that is the computer. By fixating on the processor, you show a virtual total lack of understanding of what it takes to turn all of those parts into a harmonious whole.

So, what else in a Powermac supercedes a pc? We have:


166 mhz bus (slower than either an average Athlon (266) or P4 (400)): Advantage PC.

UDMA 100: Effectively the same as a PC (not much difference between 100 and 133): Push

Firewire: Built in to all macs, many pcs still don't have it: Advantage Mac

Video: Most low end PC's do now have AGP slots, but it is still impossible to upgrade something like an iMac. At worst you can still buy a pci card for a low end pc and upgrade video or to dual monitors: Advantage PC

Sound: You can get nice sound cards for both, and while you can upgrade the sound in a cheap pc, people who buy cheap pcs or iMacs don't care about sound THAT much: Push

Monitors: Apple has nice monitors. On the other hand, the ADC system has some pretty damn expensive adaptors with them, and for what value? Why not just go DVI? Plenty of manufacturers can put the power lines in the same bundle of cords with the video signal if they want to (my KDS Rad 5 does it), but why make a proprietary format?: Push, but I wish Apple wouldn't use ADC

Harddrives: They use the same parts. Low end macs have low end drives (5400), high end macs have high end drives (7200, SCSI is you go real expensive). Ditto for PCs.: Push


So, the reason why the processor debate comes up often is because it's one of the few things that differentiates the two systems. On a side note, it is much easier to drop a $50 (and that's a more expensive one) Firewire card into a PC than it is to drop a new FSB in a mac. Right now the CPU and FSB are holding back the mac. It's the only variable that changes from it and a PC.

[pgwalsh]

Originally posted by i_b_joshua

ummmmmm.... not once.

some people on these forums just don't get it do they?

we wouldn't be reading these fourms and devoting our valuable time to answering inane statements if we were interested in PCs. we're here because we love macs. the PC/mac comparisons, whatever their value, are wasted on the majority of us.

i_b_joshua

Well said....

[dethl]

As much as I want to see moto and ibm compete...its not exactly gonna be a level playing gound. Moto is coming out with a 32-bit processor while IBM has a 64-bit one...if the people realize this...moto is out of buisness

Sorry moto...you have been too slow in producing new chips...and now its coming back to bite you on the a**.

[copperpipe]

Well, it seems to me that most of the people that reply to these threads aren't looking at the whole picture, and the threads just turn into these silly pissing contests. Now this thread was at least enjoyable to read in some ways, and I think a lot of thoughtful arguments have been made. And yes, I too think that Apple's last nut to crack is a super powerful processor that upgrades "with the times". And I would love it if they kept their original G3 imac, and priced it down to $500-$600 for people with smaller wallets, but that's besides the point. These new processors look like they could be the ****, but I just bought the dual 867, and I can say this thing kicks some serious booty, and i couldn't be happier with it's speed/dollar value. (and of course the OS is just king) So in my mind Apple has good offers currently, and it looks like it has a nice future ahead. The Steve Plan has been worked on for some time now, and it's really coming together. Get us that last nut, and watch Apple soar!

[Frobozz]

"166 mhz bus (slower than either an average Athlon (266) or P4 (400)): Advantage PC."

This does not give the PC an advantage. It _can_ make it faster in some circumstances, but it's not a simple matter of 400 MHz bus being 3 times faster than our 166. The PC, in the case of a 400 MHz bus, is really only supplying 3 or 4 buses at lower bandwidths-- like 100 Mhz x 4. Because of how a PC is built, EVERYTHING goes through the system bus in both directions. So in the PC's case, 167 MHz a single direction, and adding another 167 for the other direction, for a total of 333. In most cases on the Mac, the CPU, memory, and hard drive/device controllers can bidirectionally talk. This means that in most cases a 167 bus Mac is as fast as a 333 Mhz bus PC. The only Caveat is the amount of information it can send at that speed. The PC will have a slight advantage because of the through-put (more GB/sec), but it's through a smaller pipe. Keep in mind that a Mac can have it's memory talk to the CPU in a more direct manner, so these types of things are not as much of an issue on the Mac as the are for a PC.

I read most of this on other rumors sites, so if there are small errors I apologize in advance.

[eric_n_dfw]

Originally posted by Frobozz
"166 mhz bus (slower than either an average Athlon (266) or P4 (400)): Advantage PC."

This does not give the PC an advantage. It _can_ make it faster in some circumstances, but it's not a simple matter of 400 MHz bus being 3 times faster than our 166. The PC, in the case of a 400 MHz bus, is really only supplying 3 or 4 buses at lower bandwidths-- like 100 Mhz x 4. Because of how a PC is built, EVERYTHING goes through the system bus in both directions. So in the PC's case, 167 MHz a single direction, and adding another 167 for the other direction, for a total of 333. In most cases on the Mac, the CPU, memory, and hard drive/device controllers can bidirectionally talk. This means that in most cases a 167 bus Mac is as fast as a 333 Mhz bus PC. The only Caveat is the amount of information it can send at that speed. The PC will have a slight advantage because of the through-put (more GB/sec), but it's through a smaller pipe. Keep in mind that a Mac can have it's memory talk to the CPU in a more direct manner, so these types of things are not as much of an issue on the Mac as the are for a PC.

I read most of this on other rumors sites, so if there are small errors I apologize in advance.
Maybe I'm ignorant - but I thought I knew quite a bit about such things - and what you are saying doesn't make sense to me. Maybe I'm not understanding your choice of words.

The way I understand the newest PMac arcitectures (in the simplest of terms), the G4's can talk to the rest of the machine at up to 167Mhz - period. They don't have DDR capabability. The memory controller directly in line with them talks 167 out one end (to the G4's) and 167 DDR out the other to the RAM. It also connects to the main, system bus and talks 167 (or slower) to the PCI slots and other parts of the machine.
The nice thing about that controller is that it can (theoretically) handle DMA hits to RAM and, since the DDR RAM has twice the bandwidth, less cycles are stolen from the G4's when it does so. (I don't believe the PCI, firewire, ATA or any other busses are DDR capable - but I may be wrong.)

As far as single vs. bi-directional, I'm not sure what you are talking about. The clock ticks on the bus and info is send. On the DDR RAM bus, info is sent on the low and high voltage cycles, effectively doubling the througput of the bus. But there is no way (that I know of) for data to go "both ways" on any given clock cycle (or 1/2 of a cycle for DDR)

Please enlighten me if I am wrong about any of this.

[Bregalad]

Originally posted by kenohki


WTF? "Agressiveness of your memory system and it's latency"? You can't adjust that. First off, latency of memory is not adjustable. It just depends on what you buy, whether it's DRAM, SDRAM, MoSys 1T-SRAM or whatever. Memory latency is determined by the materials and build of the actual memory. And I'm not sure what you're talking about by "agressiveness" but I'm assuming it's something to do with paging but could you expand a little on this?

What the original poster meant was that no matter what quality of RAM you buy for your Mac it'll still run at the slowest CAS 3 timings (2.5 in the case of the new DDR models). On the PC sticking high end CAS 2 5-2-2 1T PC2700 DDR into your PC and adjusting the memory settings in the BIOS accordingly will yield a measurable performance improvement over standard CAS 2.5 stuff.

For the overclockers there is an additional benefit to buying expensive RAM. I read a test report in which a 1.6GHz Pentium 4 that ran at 2.2GHz using ordinary DDR was able to run at 2.5GHz using top of the line PC3200.

Essentially this all boils down to choice. Whereas there are definite compatibility advantages to Apple's control of the entire widget, the sheer number of choices in the PC world results in rapid technological advances and, at the same time, very aggressive prices.

You could spend $30 on a PC case complete with a 300W power supply. You could also spend $300 on the case alone. The same holds true for many other components. It's not difficult to build a PC with very good components and a fit and finish quality that rivals that of a Mac. Notice I said build. Buying a PC off the shelf means you have to accept the component choices and manufacturing quality of whoever had the lowest bid.

PC motherboard manufacturers have to compete with one another on features like built in FireWire and ATA-133 RAID. They also compete on BIOS features like automatic updates via the internet and the ability to adjust the timing of virtually everything. The result is great for consumers. Not only are prices very low, but features are often available before you can even make use of them. Serial ATA is the latest example while FireWire is probably the only case of the PC world being behind Apple.

Finally there is one other thing that will always make building a PC, whether it be a $300 peecee of crap or a $2000 gamer's ultimate, much less expensive than a Mac: OEM parts. The serious PC builder who selects each component individually does not need the "nice" features that come with a retail box so she is able to save a lot of money getting the same hardware without the glitz.

When Mac clones and CHRP were announced people had visions of building their own Mac using the best parts they could afford. That dream was soon shattered and today we're back where we were in 1995 paying through the nose for an operating system and a better than average case design. Oh and Steve, why did you put those ridiculously loud, 60mm, high rpm fans in the new MDD case? I thought you wanted Macs to be seen and not heard.

Lest you think I'm a PC weenie, I own 4 Macs and have been running OS X since developer preview 2.

[g3ski]

come on now folks, Mhz myth or not, you all would prefer to have a dual G5/2.8Ghz system right now.

And for processing video and 3D, mhz do make a difference. The fastest graphics boxes run Intel and AMD chips. Macs are just not there. This is not my opinion, it's not PC hype, and it's not Mhz myth. It's a fact. Our Macs at 1.25Ghz cannot compete with 2.8Ghz PCs with 533Mhz front side buses....and it's sad, sad, sad.

Blame Motorola for this issue, once again, just like when we were stuck at 500Mhz for 18 months. Apple could only PR their way out of the Motorola mess. Blame Motorola, not someone on this forum who wants a faster mac....all they want is a faster mac.

We need a faster front side bus on the PPC 74XX/75XX chips!

We need new chips....give me G5 and G6 in volume or the IBM 970!

[locovaca]

Originally posted by Frobozz
"166 mhz bus (slower than either an average Athlon (266) or P4 (400)): Advantage PC."

This does not give the PC an advantage. It _can_ make it faster in some circumstances, but it's not a simple matter of 400 MHz bus being 3 times faster than our 166. The PC, in the case of a 400 MHz bus, is really only supplying 3 or 4 buses at lower bandwidths-- like 100 Mhz x 4. Because of how a PC is built, EVERYTHING goes through the system bus in both directions. So in the PC's case, 167 MHz a single direction, and adding another 167 for the other direction, for a total of 333. In most cases on the Mac, the CPU, memory, and hard drive/device controllers can bidirectionally talk. This means that in most cases a 167 bus Mac is as fast as a 333 Mhz bus PC. The only Caveat is the amount of information it can send at that speed. The PC will have a slight advantage because of the through-put (more GB/sec), but it's through a smaller pipe. Keep in mind that a Mac can have it's memory talk to the CPU in a more direct manner, so these types of things are not as much of an issue on the Mac as the are for a PC.

I read most of this on other rumors sites, so if there are small errors I apologize in advance.


Not to come off as a pompous ass or anything, but I really suggest that you take a computer engineering class instead of taking what someone dumbed down from what someone dumbed down from a similar situation and posted it. Not to be arrogant, but to prove that what I'm about to say is not ************- I am currently a Senior in Computer Engineering at Iowa State University. I have taken classes on both computer architecture and processor design, as well as assembly programming and interrupt programming. We do most of our assembly on PowerPC processors, for what it's worth.

A bus transfers data. It goes in one way only at one time- there is no such thing as a bi-directional bus that transfers both ways at the same time- that would be two busses. A Pmac does this at a speed of 167 MHz. It does one thing during each cycle- it transfers data from the cpu to the system controller or from the system controller to the cpu, no more. An Athlon transfers does this very same thing at 133 MHz (soon to be 167 MHz), but it has the ability to transfer twice during a cycle- this is called DDR. So, this does twice the amount of transfers in a clock cycle in compared to the G4 bus. A P4 does this very samet hing at 100 MHz (and is now becoming 133 MHz), but it has the ability to transfer four times during the cycle- this is called QDR. So, it does four times the transfers in a clock cycle as compared to the G4 bus, or 2 times the transfers in a clock cycle as compared to the Athlon. I am not trying to twist facts in anyway. The G4 has the smallest "pipe." The G4 bus is no more efficient than the Athlon or P4 bus. Prior to the 167 MHz bus, the G4s had the same bus (size and speed wise) as the Pentium 3. The size of the busses are:

G4: 64 bit
Athlon: 64 bit
Pentium 4: 64 bit

So, bus speeds are:

G4: 64 (bits/cycle) * (1/8) (byte/bits) * 167 (cycles/second) * 1 (SDR)= 1336 MB/sec
Athlon: 64 (bits/cycle) * (1/8) (byte/bits) * 133 (cycles/second) * 2 (DDR)= 2128 MB/sec
P4: 64 (bits/cycle) * (1/8) (byte/bits) * 100 (cycles/second) * 4 (QDR)= 3200 MB/sec


A hard drive, graphics card, firewire device, usb device, keyboard, mouse, sound card, any kind of device, when it needs to transfer data, will raise an interupt with the processor. This is true of any processor in existence today with very few exceptions (and those are integrated processors that only do one function, like those in cars, and they work by polling to see when data needs to be moved around). When an interrupt is raised, the processor stops what it is doing, saves what it was doing to memory, services the interrupt, and then resumes processing. Writing to memory is a very time intensive process (relatively speaking), one that is dependant on both the FSB and memory speed. While the Pmac may have DDR 333 memory, it still has a piddly 167 MHz bus which is the bottleneck. The only difference between a pc and a mac is that the most PC chipsets are composed of two chips, with one controlling the HDD, USB, Firewire, Ethernet, etc. and the other the AGP, Memory, and CPU. That said, it does not incur any penalty versus the mac when performing CPU to Memory operations because it is still only going through one additional processing unit.


So, in retrospect, the biggest bottleneck in today's computing is... the memory bus. Memory accesses are very expensive in processors (which is why programs that run in cache run very quickly) regardless of what platform it is, and only by removing the bottlenecks between the processor and the memory can you improve performance greatly.

[g3ski]

Great info.....

But the Pentium 4 has a 533Mhz FSB, not just a 400Mhz bus. Where is that extra 133Mhz going to, coming from?

What is the difference between the FSB and the memory bus?

[Telomar]

Originally posted by locovaca


Not to come off as a pompous ass or anything, but I really suggest that you take a computer engineering class instead of taking what someone dumbed down from what someone dumbed down from a similar situation and posted it.

Blah blah blah...Just to correct a few things. The G4, Athlon and PIV all use bidirectional buses. Data can be passed in either direction along the bus, albeit not necessarily at the same time.

A unidirectional bus is something akin to what the PPC970 uses. It uses two uni-directional buses. One streams in each direction. One of the major advantages being that it allows streaming simultaneously in both directions and lowers overhead.

Second you will find the bus of the G4 is considerably more efficient that those of the Athlon or PIV. The design of it is such that the overhead is lower and efficiency greater. Unfortuantely it has the lowest theoretical bandwidth of the lot, which makes it a weak point in the desktop G4.

One of the reasons you will never see a DDR MPX bus is because to do so would mean trading off some efficiency (along with some other benefits).

Finally certain parts of the computer rely on DMA. Bandwidth from CPU to memory is not necessarily the limiting factor in those cases. This is one of the reasons that the Xserve can be a very good file server.

[locovaca]

Originally posted by g3ski
Great info.....

But the Pentium 4 has a 533Mhz FSB, not just a 400Mhz bus. Where is that extra 133Mhz going to, coming from?

What is the difference between the FSB and the memory bus?

Up until recently the P4 had a 400 mhz FSB and a 533 mhz memory clock- so it went to the same place the extra 167 mhz goes on a mac- bandwidth for other devices (which, admittidly, doesn't help very much because they still depend on the CPU for most things, and it's still stuck on that 400/167 mhz bus). Wehn Intel releases their 3.06 they will officially be moving to a 533 mhz FSB and run it at the same speed as the memory. That said, it's possible to run the memory bus and the FSB at same speeds, since they are one chip removed from each other, but the benefits are very small.

The FSB is the bus that the CPU communicates with the system controller/north bridge with. Anything that a CPU touches comes through this thing. In P4's and Macs there is only one FSB for whatever number of CPUS you throw at it (so, a dual processor doesn't have dual FSB)- the Athlon has a FSB per cpu (which isn't as grand as it would sound, but it does help).

The Memory Bus is what connects the memory subsystem to the system controller/north bridge. It operates at whatever speed your memory is set at, and while this usually runs at the same speed as the FSB, it isn't required to. The reason why it usually runs at the same speed is because there are few benefits to not running it at the same speed: if it's slower than the FSB then the processor will always be waiting on memory, and if it's faster then the memory will be waiting on the FSB. The only thing that gets sped up if the memory is faster are devices that do direct memory writes, however, even these still require CPU interaction, so they don't get a magical speedup of 2x just because there's all this extra bandwidth lying around. The memory bus doesn't even have to be the same width as the CPU- in the P4 (RAMBUS) there are actually two 16 bit memory busses or a 64 bit bus (SDR, DDR), although there are dual ddr busses coming out soon. With the Athlon this is typically just 64 bits, although NVIDIA's chipset can use a 128 bit bus (because of their integrated graphics, one of the few things that can effectively make use of extra bandwidth. An integrated graphics card that shares system memory reserves a portion of the memory for the card, and it gets exclusive rights to this memory, so it can operate on it without the CPU). The G4 has a 64 bit bus that runs at the same speed as the FSB, only this runs DDR.

So the main difference between the two is the fact that they are two seperate things with a chip in between them. While a majority of what travels on the FSB is just stuff from the memory bus, the FSB does much more stuff than the memory bus.

[mr evil brkfast]

We shall see if an when motorola gets the chips out the door... I think 2003 will be a long year like this one in terms of upgrades.

The new 970 will hopefully be the savior in these dark times.

[Chryx]

[QUOTE]Originally posted by locovaca
Up until recently the P4 had a 400 mhz FSB and a 533 mhz memory clock

Nope, PC800 Rdram clocks at 400Mhz, PC2100 clocks at 133Mhz, PC133 clocks at 133Mhz, it's not possible (to my knowledge) to use PC1066 RDram (533Mhz) with a 400Mhz-FSB P4

with the 2.4Ghz P4's introduction, they raised the FSB from 100 QDR, to 133 QDR (400 effective to 533 effective)