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

UNIX was way before the X86:

[AtariAmarok]

You said "UNIX technology was created for the x86 architecture"

First x86: "The 8086 blasted away at amazing speeds of 4.77 and eventually 8 MHz -- hardly a calculator by today's standards. All this started in 1978."

(check here)

UNIX invented: "An
interactive time-sharing operating system invented in 1969
by Ken Thompson after Bell Labs left the Multics"

(click here)

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."

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).

Re:[Q] Small & Expensive = CISCRISC?

[makapuf]

yup, microcode, that is several processor-specific RISC instructions put into a CISC instruction.

Then, RISC perormance and CISC compactness. If you want not to use CISC "huffman compression" , well use cheap instructions.

Ummm, Sun?

[Wiz]

In the high end markets, RISC CPUs from HP, SGI, IBM and Sun still dominate. x86 has never been able to reach these performance levels even though they are sometimes a process generation or two ahead. RISC vendors will always be able to make a faster, smaller CPUs. Intel however can make many more CPUs for less.

Lets see. HP and SGI have sold themselves to the Itanium 2 which is ok but is EPIC, not RISC. IBM have the Power4+ and Power5 on the way which are pretty damned good. Sun have the US3 and US3i. Sun certainly don't have a performance lead. I've benchmarked an Opteron against the US3 and US3i and it isn't pretty for Sun. The Opteron is actually MORE efficient clock for clock in 95% of tests I ran. And yes, all the tests in question were real world programs running real world data. So I disagree. Just because it is RISC, doesn't mean it is faster. Chips like the Alpha prove it is possible, but with the rate of developlment of x86 and it's compilers it is becoming more difficult for them to keep up.

Re:PPC

[JaguarCro]

Around here (Colorado), electricity is seven cents a kilowatt hour.

Well welcome to Northern California where our electricity is currently 24 cents per kilowatt hour! Now here we are talking ($36.69 x (24/7) or $126.14 per year per machine. Apple doesn't sell a dual 1.6 Ghz machine, but if you still use your comparison numbers and prices we get a payoff in less than 4 years. (and if you really were just doing CAD you wouldn't need to Superdrive or Modem which cuts the price difference now down to $270 or almost 2 years!!)

In otherwards, before a/c costs are taken into account the machine will pay for itself in just over 2 years and for the remaining 1 to 2 years it is used it will be saving the company even more money.

By these numbers alone, I would say that buying a PC in expensive electricty areas of the country is a short sided mistake that will hurt your company or institution.

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.