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Head-to-head Processor Challenge

E

eyeluvmyimac

macrumors regular
Original poster
Oct 27, 2002
229
1
With all the debate about the upcoming 970 release, and which computers will contain which processors, I felt the need to ask for a little more information on the subject.

My biggest question is, What is the difference between the 970 and a Power4?

Second, if we had say, a 1 ghz g3, 1ghz g4 and 1ghz g5, how would they vary in terms of speed. Obviously they would first would be slower than the second and so on, but why is it slower, is it just the architecture of it?

(I know the 970 is 64mb opposed to the current 32, and that will definitely make a difference, but how else is the speed effected?)

Thanks.
 
Re: Head-to-head Processor Challenge

Originally posted by eyeluvmyimac
With all the debate about the upcoming 970 release, and which computers will contain which processors, I felt the need to ask for a little more information on the subject.

My biggest question is, What is the difference between the 970 and a Power4?

Second, if we had say, a 1 ghz g3, 1ghz g4 and 1ghz g5, how would they vary in terms of speed. Obviously they would first would be slower than the second and so on, but why is it slower, is it just the architecture of it?

(I know the 970 is 64mb opposed to the current 32, and that will definitely make a difference, but how else is the speed effected?)

Thanks.
Click to expand...

OK, in order:

1) The 970 has Altivec, has only one processor per chip, and has much less cache. There are a few other changes, but nothing too major that I know of.

2) It's hard to say. The G3 is quite a different chip from the chip it once was (750fx instead of 750). I would guess it would be a little slower than a G4+ and it wouldn't have Altivec. It would be a little faster than an original G4 (if you could get a 1GHz original G4). The PowerPC 970 (probably the G5) will be at least 20% faster (except on Altivec) and at most something like 4-5 times as fast (for things that are ONLY limited by memory speed). It will be a little slower on Altivec tasks that aren't limited by memory speed. The "64 bitness" of it will actually slow it down slightly for most tasks (very few things need 64 bit integers, and they take up more space).
As for why, the G4 has level 3 cache, Altivec, and a more advanced bus (the new G3s support a 200MHz bus, but don't use it quite as effectively, and it isn't used in any Apple products). The 970 has twice as much floating point power, can reorder instructions if they aren't in an optimal order (very useful on crappy PC ports of programs since they usually are poorly optimized), has over 4 times as fast memory, twice as big a level 2 cache, and can handle more instructions at a time.
 
eyeluvmyimac:

(I know the 970 is 64mb opposed to the current 32, and that will definitely make a difference, but how else is the speed effected?)
Click to expand...
You meant 64-bit and 32-bit.

Second, if we had say, a 1 ghz g3, 1ghz g4 and 1ghz g5, how would they vary in terms of speed.
Click to expand...
Well in general the PPC-970 (G5?) would destroy the other two in most anything, the G4 (assume 7455 model) would beat the G3 (assume 750fx model) in the AltiVec stuff, and the G3 would beat the G4 in the non-AltiVec stuff.

My biggest question is, What is the difference between the 970 and a Power4?
Click to expand...
They took off a lot of processor cache, removed the second processor core, changed the system interface, and added AltiVec units.
 
Originally posted by übergeek
970 would be faster than both the G3's and the G4's.
Click to expand...

You can't just say that.

There is no Straight answer.
In things using the SIMD structure the 970 would beat the G4 and the G3 has no SIMD right now so in THAT test it would win.

If apple release a 1GHZ G3 (which they could) it would kick the G4 handily in non Altivec (SIMD) tasks because of the smaller pipeline (smaller = better). I belive the 970 would beat the G3 in that test because it is faster and has many other features aready mentioned.

If the G3 got an Altivec it would own. But IBM/Apple didn't want a last generation chip coming back again (to eat the G4 alive).
 
thanks for all the info guys, but what are Altivec and SIMD, and why would it make a G3 eat the G4 alive?
 
lol yea, i forgot to post that its probably (and now confirmed) to be a very dumb question but I really don't know. Sorry. I know, i sound like a complete moron -- i really am not, only partially =)
 
Originally posted by eyeluvmyimac
thanks for all the info guys, but what are Altivec and SIMD, and why would it make a G3 eat the G4 alive?
Click to expand...

SIMD is a way of doing one instruction on more than one number at once:

non-SIMD: A = A + 1, B = B + 1, C = C + 1, D = D + 1 (4 operations)

SIMD: A,B,C,D = A,B,C,D + 1 (1 operation)

Altivec is the particular SIMD instruction set Apple uses. The G3 wouldn't eat the G4 alive because of SIMD (the opposite is true). The G3 is a simpler chip though, which means that it can sometimes do non-SIMD stuff a bit quicker (it takes a G3 4 stages to do something and a G4 7 stages. In many situations this doesn't matter, but if something messes up in the first stage, the mistake goes through the rest of the stages, wasting time). Because of other enhancements the G4 has, I still think it would win against the G3 (particularly the MPXBus and the L3 cache, the G3 still uses the 60x bus from early PowerPCs).
 
Originally posted by Catfish_Man


SIMD is a way of doing one instruction on more than one number at once:

non-SIMD: A = A + 1, B = B + 1, C = C + 1, D = D + 1 (4 operations)

SIMD: A,B,C,D = A,B,C,D + 1 (1 operation)

Altivec is the particular SIMD instruction set Apple uses. The G3 wouldn't eat the G4 alive because of SIMD (the opposite is true). The G3 is a simpler chip though, which means that it can sometimes do non-SIMD stuff a bit quicker (it takes a G3 4 stages to do something and a G4 7 stages. In many situations this doesn't matter, but if something messes up in the first stage, the mistake goes through the rest of the stages, wasting time). Because of other enhancements the G4 has, I still think it would win against the G3 (particularly the MPXBus and the L3 cache, the G3 still uses the 60x bus from early PowerPCs).
Click to expand...

Too bad that IBM has a chip that is like the G3 execpt runs at a GHZ and has read DDR support (not fake). And the bus was improved. But you are right that the Current G4 have major advanced since the old G3.

It's just that apple probably will not use the IBM G3 improvments for facts like it will confuse the hell out of people.

Edit: to clarify the 'eat the G4's sales' buisness. IF THE G3 Had and SIMD support it would kick the G4 easily (well execpt for oldish technology, read above, IBM has made a newer one).

Things that bennifit from SIMD are apps like Photoshop. Because of the G4's SIMD it would beat the G3 in most senerios. Because of real world applacation (sp) the G3 isn't the chip is could be. There are many things that IBM could have done to make the G3 survive, just as another processor option, but they didn't/
 
SPEC Benchmarks

If you go by the so-so G4 benchmarks on the various SPEC Tests, the 970 would be around 2x~4x better than today's G4s I beleive...also, the 970 has two individual Altivec units compared with one in the G4....

Lets put it this way, if the 970 was clocked up to 3.0 GHZ, it should be scoring around 1800~1900 (fpu) on standard benchmarks, compared to 1200(fpu) on P4 3.0GHZ...thats WITHOUT ALTIVEC.

At 1.8G it already scores, what was it, 1100?
 
Originally posted by MrMacman


Too bad that IBM has a chip that is like the G3 execpt runs at a GHZ and has read DDR support (not fake). And the bus was improved. But you are right that the Current G4 have major advanced since the old G3.
Click to expand...

The IBM 750fx (the newest G3 they make) has a 200MHz 60x bus (which supports PC1600 DDR, although it's an SDR bus). If I was talking about the old G3 I would have mentioned its crappy 603 style FPU. If you know about some other G3+enhanced bus chip please post a link, I haven't heard of it. Also, the current G4's DDR support isn't fake, it's just inadequate. It still improves performance (by reducing latencies and allowing DMA that doesn't take away from processor bandwidth).

also, the 970 has two individual Altivec units compared with one in the G4....
Click to expand...
The G4+ has 4 Altivec units and can send instructions to (iirc) 3 of them at a time. The 970 has the same number, but is limited to old G4 style instruction dispatch.
 
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