Analysis: x86 Vs PPC

Gentu writes "Nicholas Blachford (engineer of the PPC-based PEGASOS Platform) wrote a long and detailed article, comparing the PPC and the x86 architectures on a number of levels: performance, Vector processing and Power Consumption differences, architectural differences, RISC Vs CISC and more. The article is up-to-date and so it takes the G5 into account too."

Comments

These arguments are so tired

[uradu]

This isn't the '80s anymore where performance is the most critical issue and we jump platforms every time a faster architecture comes out, since we don't have a large software base anyway. Nowaways software IS the more important aspect, and only relatively few well-heeled, game-addicted geeks are going to jump on the PPC just because it's a fews ticks faster this week, and Jobs winked at them with that very special smile. Given the way this industry goes, IBM/Motorola will sit back again, wipe the sweat off their foreheads and take a breather, and before you know it, Intel/AMD will have a faster processor again.

If you have x-platform software that will compile painlessly on either architecture, go for it, switch with each faster chip. But for most others, I doubt performance rants like these will make much of a difference. After all, how many Mac users switch to the PC just for the performance during those stretches when the PC has the upper hand?

Re:These arguments are so tired

[Hard_Code]

Did you even read the article? It is not about how PPC is faster than x86. It's about how PPC is more *efficient* than x86 which leads in the long term to lower power usage, whereas x86 gets diminishing returns on ramping up their clockspeed and playing games shuffling registers, etc. He specifically mentions that CPU speed is not really as critical as the companies make it out to seem because there are diminishing returns due to other system components. He mentions that x86 is up against a thermal wall by 2004 although I don't know where he got that data (it may be in a footnote but I not going to go back just to check). Speaking as a gamer who runs a pretty loud machine that overheats in summer, I am VERY interested in chips becoming cooler, moreso than them getting faster (the hard work is typically shoved off onto a graphics card).

Truly suprising colnclusion, OR NOT!

[pbox]

Nicholas Blachford (engineer of the PPC-based PEGASOS Platform) says that the PPC is better than x86.

What an unbiased opinion. Maybe we should really hear the other side too. I like the article for the wealth of info, and we all know the shortcomings of the x86 platform, but the conclusion seems to be biased.

Or is it just me?

A good OS...

[svenjob]

...makes all the difference. The thing that made me switch to PPC was, without an effing doubt, MacOS X. I went from an Athlon 2400+ with 768MB RAM to a home-made PowerMac 800 with 512MB RAM. I cut my processor by a 3rd and lowered my RAM. What did I gain? An amazing OS. If RISC processors continue to get more and more into the same processing spectrum as x86's, I think that OS X will help draw in the masses. Another thing that would help would be increased yields. That would lower prices and increase market share. Anyways, if x86 had OS X, I probably would have stayed with x86. But since it doesn't, I didn't.

Re:how long can x86 go?

[Blob Pet]

Which dies first, BSD or x86?

An interesting viewpoint

[downix]

From my experience with RISC CPU's is that rating them by Mhz is often times the way to not understand what makes a RISC a RISC and a CISC a CISC.

Let me explain by example.

My MIPS R4400, running at around 120Mhz, I believe, runs circles around my Duron 750Mhz machine here. This is while the R4400 uses sDRAM vs DDR-RAM in the Duron, and the R4400 uses older plain-jane IDE while my Duron runs ATA-100.

I find it nice to boot up my old Indigo2 and play around, it responds so nicely, and renders quite well.

Re:An interesting viewpoint

[uradu]

> rating them by Mhz is often times the way to
> not understand what makes a RISC a RISC

What you mean is that you can't compare RISC MHz to CISC MHz--or any design's MHz to any other design's MHz, for that matter. Your statement in fact reveals that YOU don't understand RISC, because MHz are a much more reliable metric for RISC than for CISC CPUs. That is because by the very definition RISC CPUs tend to take a constant amount of ticks per instruction, which is not the case for CISC. So yes, comparing two RISC CPUs that both execute one instruction every two cycles on a MHz basis will give you a pretty good comparison of their relative performance.

Re:how long can x86 go?

[Elwood P Dowd]

You could say that right now, "The x86 is not dead, because the RISC processors that replace them have a CISC compatibility layer".

The P4 decodes the larger, more complex x86 instructions into smaller chunks for use inside the processor, which is more or less RISC in its core. The CISC vs. RISC debate is kindof over, because both CISC and RISC chips have been adapted to gain the advantages of each others' design principles. Even the PPC 970 has to decode some of its "RISC" instructions into separate micro-instructions for execution.

The only chip design methodology that still has its original meaning is VLIW. That original meaning is "bankruptcy."

[Q] Small & Expensive = CISCRISC?

[4of12]

When Microprocessors such as x86 were first developed during the 1970s memories were very low capacity and highly expensive. Consequently keeping the size of software down was important and the instruction sets in CPUs at the time reflected this.

So I'm puzzled. Perhaps someone can enlighten me on this.

If CISC is particularly appropriate for memory that is

1. low capacity, and
2. highly expensive

why doesn't the same argument apply to CPU's with no main memory per se, but just a good sized L3 cache?

Modern cache memories are, guess what,

1. low capacity, and
2. highly expensive

so it would seem to follow that higher performance could be got by using a CISC model.

Since main memory latency and BW are pretty limiting, I half expect that there's good argument to make very high performance systems live completely inside a large cache.

970 is a real superscaler

[norwoodites]

the 970 can have more than 200 instructions in flight at the same time, it can finish up to 5 instructions each clock (4 if there is no branches).

Check your facts, please; G5 IS low power

[LionMage]

Each g5 dissipates a whopping 97 watts

No, two G5 (PowerPC 970) processors together dissipate 97 Watts. Each individual processor dissipates about half that.

Don't believe me? Check out this chart on ArsTechnica. (The heading for the chart reads "Preliminaries: die size, power consumption, and clock speed.") A single 1.8 GHz PowerPC 970 dissipates 42 Watts. So a single 2.0 GHz PowerPC 970 dissipates a little more than that; therefore, it's reasonable that two of them would dissipate somewhere between 90 and 100 Watts, total.

The EE Times article you cited is highly inaccurate. They only look at the total number of fans in the G5 machine, and forget the fact that these are low-RPM fans and are software controlled per-zone to regulate temperature. Low RPM means less volume of air moved per unit time. So the design tradeoff that was made, clearly, is to have more fans running slower in order to keep noise levels down and to target cooling for each zone appropriately.

This is why it's a good idea to check multiple sources for your facts. Then again, if your goal was to present a very distorted version of reality to fit your goal of painting the G5 as a power hungry monster, you would very carefully choose your source of information so that it seems to support your assertion.