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A nice bit of info about the 7455 1Ghz processor

K

KingArthur

macrumors regular
Original poster
Jun 15, 2001
236
0
Marion, Ohio
We now have:
"Full symmetric multiprocessing (SMP) support – Allows customers to easily scale their designs with multiple processors to deliver much higher system performance
More block address translation (BAT) registers – increased from 8 to 16 to support efficient embedded operating systems through high speed mapping of additional large blocks of data.
Cache Locking – Cache way locking has been added to the L1 caches, allowing key performance algorithms and code to be locked in the L1 cache. Continued support of the L3 cache on the MPC7455 helps assure system compatibility for customers of Motorola’s MPC745x products" (quoted from motorola's website).

Now we can have G4 computers with up to 32 processors working semetrically. This means that people wanting to push the G4 to its limits can do so with style. (you wouldn't even need a heater in that room!) I know Apple won't make models over probably 2 or 4 processors, but the 1Ghz 7455 is only $295 when bought in quantities of 10.

Also, the new motherboard has 2MB of L3 cache running at 500Mhz per processor! This beats the hell out of DDR RAM on P4s except the 7455 can only support 2MB of L3 cache.
 
More interesting yet: The MPC 7450, which is currently in the PowerBooks, dissipates 14 watts at 533 mhz. The Apollo G4, on the other hand, dissipates 10 watts at 666 mhz! Meaning we'll have faster powerbooks with longer battery life in the not-too-distant future. I drool at the very though...
 
The high-end PCs do not support L3 Cache, but their support for DDR Ram gives them an advantage over the G4. I believe though that the DDR Ram runs at 266Mhz where as the L3 cache now runs at up to 500Mhz (1/3 processor speed on pre-Apollo models). This basically is like having the backside, 1/2 processor speed L2 cache from older computers, just in 2MB amounts per processor v.s. the 1MB limit on L2. Plus you have the on-chip L2 and L1 cache running at full processor speed, so you basically have a large L1 cache routed through a smaller L1 cache. Although this is not the exact physics, it does provide some basis for average people to go by.

Also, most top-of-the-line PCs have about 320k of on chip L2 cache, which does beat the G4, but the G4's L2 cache is comparitively faster because the PCs must break the instructions down into smaller units to process whereas the G4 can take the more complex instructions without having much of a performance hit.
 
Re: If I have the Moto # scheme right:

Originally posted by mischief
This is our first actual look at the specs (MPC8540): url:[http://e-www.motorola.com/webapp/sp...?code=MPC8540&nodeId=03M943030450467M0yqX0l0H ]
Click to expand...

Not quite... As I understand it, this document refers to a sort of 'G5 lite' intended for 'embedded' uses. It draws very little power and (I think) would be used in things like network routers and cars. In what ways it's different from the real McCoy I don't know. The specs certainly look impressive in themselves...

I presume the G5 will be launched with a clear 8500 model number?
 
Xeon Line

The Xeon line from intel has a large full speed L2 cache in it, I think it goes up to 2MB. They use them in the high end server line, intel makes a lot of money off these high priced babies. As far as L3 I am not sure.
 
P4 cache

There is less of it, but it runs at full clock speed. The front side bus speed of the P4 is 400mhz (100mhz quad pumped - yes it works).

DDR ram is used on some mobos running at up to 333mhz.

There is a memory bottleneck on anything short of Rambus memory (currently at 600 and 800mhz speed).

We have a 2.2ghz dev system here at work. The thing screams, even with XP. Lots overclockers are getting 3.1 -3.6 ghz using watercooling (essentially self contained condenser refrigerator systems) or Liquid Nitrogen.

When I sell my PC and get a G4, this will be what I miss most. The OC'ing scene.

Maybe its time for a Mac HardOCP!
 
clarification

Front Side Bus is what connects the CPU to the memory. Todays PCs have lots of bandwidth compared to the Mac, but the CPU speeds are so high there is still a bottleneck. True potential is not being reached.

A further bottleneck comes down the bus in the I/O systems in PCs. Serial ATA and PCI-X or 3GIO will solve that. These are things we will see in 2003 if not this year.

I think Apple needs a $10,000 super machine. The G4 will be fine for people like us, but the G5 needs to be an SGI MIPS killer. G5 needs to make the Sun set.

I want Apple to create three tiers:
iMac - consumer
G4 - power users
G5 - ultimate 64 bit bliss, multi processors, cost is no object creative tools.
 
Re: P4 cache

Originally posted by lewdvig
Lots overclockers are getting 3.1 -3.6 ghz using watercooling (essentially self contained condenser refrigerator systems) or Liquid Nitrogen.

When I sell my PC and get a G4, this will be what I miss most. The OC'ing scene.

Maybe its time for a Mac HardOCP!
Click to expand...

There are lots of people OC'ing Macs.. I read about PowerMacs overclocked all the time. There are many sites which are dedicated to this subject.. Heck I even OC'd my iMac.. just to name one off the top of my head:

www.xlr8yourmac.com

You'll find links off there to hard core OC sites.
 
another point

Someone mentioned the way PC CPU break instructions down. Modern PCs also have SIMD (single instruction multiple data) commands like Altivec.

Where Altivec is first gen, SSE2 is 3rd. Have a look at Toms Hardware Review for a detailed description of how this works.

The performance gains using P4 SIMD is INCREDIBLE! Its architecture is also is also optimized in a unique way.

Rubenstein did an interesting comparison of approaches. His key arguement regarding the cost of instruction mis-predicts is iffy. Also the speed in which instruction pipelines are filled was not accurately portrayed. It is currently more than double the speed because FSB and I/O speed need to be factored in. 800mhz ram sent through a 400mhz bus to a 2.2ghz CPU is faster than 133/133/1ghz.

In streaming applications mispredicts simply do not occur with the kind of frequency needed to slow things down (encoding media is something which the P4 ownz).

When I get my G4, I will do some 'absolute' benchmarks.
 
SSE2 is super fast, but my understanding is that apps need to be rewritten to take any advantage of it at all. This is unlike the G4 where even non-G4-specific apps will still benefit AltiVec, just not as much as if they were optimised for it.
 
not true

A big chunk of SSE2 is an expansion of MMX instructions. Anything written to take advantage of MMX should benefit.

As far as new optimizations go, you get the free MS VC++ compiler plugin and you are set. The ambitious like to hand code, but it isn't absoltely necessary.

Does the G5 have Altivec 2?

Listen, the huge PC market means that cool hardware usually gets there first (133 ATA, DDR, 6channel sound cards). I have a lot invested in that stuff and I am switching to the Mac.

OSX=best OS - elegant and powerful
But what has really sold me are the digital hub apps.

The thought of sending my Grandmother a photo book of her great grandson is too much to pass up.
 
Just a thought

Remember when Lockheed Martin had their "skunk works" program? It was where a lot of black projects were nursed. Projects that culminated into aircraft like the SR-71 Blackbird. The fastest plane ever. Wouldn't it be cool if Steve Jobs let some of the engineers create a "skunk works" at Apple? Imagine what they could come up with if let loose.
 
A correction to Beej:
The only reason that non G4-specific apps take advantage of SIMD processing is that OSX will use AltiVec when such things as a window popping-up or resizing/scaling. This only benifits the programs to a minor extent (but some is better than none).

Also:
AltiVec may be 1st generation, but most engineers prefer it over SSE2 because it is more efficient. Check arstechnica.com for more info to why this is (it would take forever to explain here).

Also Also:
I have heard of a MacSE/30 OCed to 1 Ghz (nitrogen cooling system nevertheless). Much of Intel's strategy revolves around using the same processor for 4-5 different speed systems, just underclocking the processor to run at a slower frequency. Basically, if you buy a P4, unless it is the new 2.2 Ghz series, just get a slower one, buy a PCI Fan, and overclock it to your heart's extent.

Also Also Also:
I agree with lewdvig about the OS being the primary thing keeping me with the mac.
 
Some things that need correcting...

...
1) SSE2 is only third generation because Intel repeatedly screws up SIMD. The P4 has one Floating Point pipeline that is shared with SSE2. The G4 has 4 SIMD-only pipelines being fed by 32 128-bit registers. At SIMD, nothing can compare with the G4 (Unfortunately, the rest of its hardware is pretty weak).

2) If you're going to overclock something, overclock an AthlonXP. The P4 has a locked processor to FSB ratio, so the only way to overclock it is to overclock the bus. This may not sound like a bad thing, but the PCI bus's clock is tied to the FSB, so overclocking the FSB screws up all the PCI stuff. AthlonXPs are way easier to overclock safely.

...and a question. Is the 10 watt Apollo the 7455 or the 7445? If it's the 7455 then the 7445 draws even less power, and it goes to 800MHz. It doesn't have the L3 cache though.
 
:^)

Regarding overclocking:

Its not quite so simple. Rather than underclocking, Intel and AMD use speed grades (savy OC'ers learn to identify these quickly). Certain yields outperform others. As new technologies are rolled out (smaller die size, copper interconnects, SOI) the speed grades are ramped up. You really need to know what to look for.

The Athlon C 'AXIA' stepping come to mind. A 900mhz CPU that could be air cooled to 1600 easily (if you consider a huge Kanie Hedgehog copper heatsink with 7200rpm fan easy). With a condenser system 2100, and with nitrogen 2500.

Crazy!

Most motherboards in the lat year have shipped with North bridge fans and sinks (memory controller). The Southbridge (PCI controller) typically does not need cooling.

My AXIA is running a stock 1100 (they ranged from 900-1200) serving files through maclan to this little iMac. I love this thing, can't wait to get a G4!
 
catfish man

You can get a lot from FSB OC'ing a Northwood since it is essentially just 100mhz bus (quad pumped). I like (have actually) AMD stuff too, but the new P4 rocks.

Good mobos have the ability to change the PCI ratio to keep it close to 33.

As a pro audio developer MMX served us well, back when the 604 was champ at Apple. I wouldn't be too harsh on it.

SSE sucked.

SSE2 is pretty cool.

In terms of FLOPs I have seen the new G4 numbers. Hey, I'm sold but I can't figure out why a good P4 system can do 300+ fps in Q3 at 6*4 Fastest and a dual G4 gets <200. Is it a driver issue?
 
Re: catfish man

Originally posted by lewdvig

In terms of FLOPs I have seen the new G4 numbers. Hey, I'm sold but I can't figure out why a good P4 system can do 300+ fps in Q3 at 6*4 Fastest and a dual G4 gets <200. Is it a driver issue?
Click to expand...

Apple says a DP1GHz gets 15GFlops, I've seen 7.6GFlops on Altivec Fractal Carbon Demo. Also, I've heard of DP800s getting 250+fps on QIII, I don't know what the settings were though. I still agree that for most stuff (read that as "anything that doesn't use Altivec a lot") the P4 is faster. The faster bus and RAM and the enormously higher clockspeed manage to keep it ahead despite being less efficient. I'm waiting for the G5, the G4 really wasn't designed to compete against the P4. It was designed to be competition for the P3 while still being able to be used in embedded stuff.
 
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