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

[AT]

software IS the more important aspect

Yes, and software is becoming more and more portable.

As the article observes, Linux (and open-source software in general) is not locked into the x86 architecture like Windows is. The use of server-side Java is growing, also architecture agnostic. Additionally, the web and web-based applications have shifted much of the work custom client applications used to do into the browser. Once again, architecture is doesn't matter.

The trend is that CPU architecture as a means of lock-in is declining, due those factors and many others. At some point, the cost of moving to another architecture will decline to near-zero, and the CPU business will shift to more of a commodity market, where people will buy on merit alone.

The only question is when it will happen; people have been predicting it for years (remember when NT ran on PPC, MIPS and Alpha?).

Right now, the PPC seems to win in some areas (power consumption, die size) and, barring architectural lock-in, it would probably take a large chunk of the Intel/AMD market.

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?

Re:Truly suprising colnclusion, OR NOT!

[stevew]

Yep, and he is still stuck back in the 80's with his RISC vs CISC arguments. He says that internally they pretty much look the same (which they do) but they're some how different because RISC is easier to make happen.

Well - today's RISC's aren't very RISCy anymore. ;-) Todays CISC's have the same aspect. The machines have all migrated to simpler cores running VERY fast, but then tagging on features like predictive branching, out-of-order execution, etc.

An example of where the guy goes wrong is in his discussion of the compilers. What he fails to understand is that one BIG reason that the Intel compiler is better than GCC is that the same kinds of compiler optimization that accounts for how the hardware schedules things work for both the PPC and the Intel architecture. This has been true since the original entry of the MIPs architecture for goodness sake. Intel KNOWS what the hardware is going to do, and built those smarts into the compiler! You can do the same thing for the PowerPC by the way..not saying you can't.

Nuff said - it was an interesting article but bowed to much towards RISC is Great - All Hail RISC bunch.

"Desktop" weasel word. Where's the Opteron?

[Anonymous Coward]

The current desktop PowerPC and x86 CPUs are the following:
x86
AMD Athlon XP
Intel Pentium 4

PowerPC
IBM 750xx (G3)
Motorola 74xx (G4)
IBM 970 (G5)

I don't care if it's marketed for servers, just look at the cost: If you can afford a P4, you can probably afford an Opteron on your desk right now. If you can afford a G5 on your desk, you can definitely afford an Opteron on your desk.

Saying the Pentium 4 and Athlon XP are the current x86 chips, is just plain wrong. Those chips are obsolete except for very low-end (i.e. under $1k) systems. If you're building a x86 machine and your budget is approximately the same as the budget of a guy building a mid-range PPC system, then you have to be crazy to not get an Opteron, desktop or not. Thus, Opteron is the chip this author should be comparing to.

how long can x86 go?

[cheezus]

I remember years ago there being talk of the x86 never being able to keep up because it would just get hotter and bigger.... but now they're over 3ghz... was that all just hooey, or will there be a point where the x86 is dead and the RISC processors that replace them just have a CISC compatibility later?

[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.

Re:PPC

[RzUpAnmsCwrds]

There are low power x86 processors. The Opteron, for example, draws around 55W for the high-end model. The Athlons aren't so bad either - around 65W depending on the model. P4 ranges from 60 to 100W, also depending on model.

Remember, electricity is pennies a KWh. Now, there are cooling considerations too, but even those are managable. In general, the highest operating expense of a company is not cooling or electricity but other factors like the facility, staff, or bandwidth.

Around here (Colorado), electricity is seven cents a kilowatt hour. Say a P4 @ 90W does the same work as a G5 @ 30W. That's a savings of 60W. Imagine the computer is on 10 hours a day, five days a week. That's a savings of 3000Whr (3KWh) or 21 cents a week. You save a total of $10.92 per year. Or, say the computers are on 24/7. That's a total of $36.69 per year.

Say an HP XW4100 system (P4 3.2CGhz) system does the same work in a CAD app as a dual 1.6GHz G5 system (remember, most CAD apps are not dual-processor optimized). The XW4100 is around $1500; the "low-end" G5 is $2000. At $36.69 per year (running 24/7), the G5 will pay for itself in 13.62 years.

On the Tclk myth

[curious.corn]

Let's all remember that the MHz jump by intel was quite a marketing op. Consumers need an easy metric to evaluate goods (Hp in cars... btw, I wonder why people don't use Watts; must sound dull, dimensioning a car on a lightbulb unit) and intel chose to give one. They went as far as re-designing their machines around the pre-condition of high clock freqs. Take a P4 and clock it to 300 MHz (assuming it would run at those speeds and not bleed all charge out of it's gates), I don't think it would perform anything decent.

Re:On the Tclk myth

[Moridineas]

You make that sound so much worse than it actually is.

We know that as chips get more complicated they get harder to scale to faster speeds. The P4 was a chipdesign that, from the beginning, was designed to scale--huge pipelines, etc (and the pipes are getting bigger too).

Now what's wrong with making a chip that is easy to scale?

Re:PPC

[pmz]

There are low power x86 processors.

Generally, they do not perform like the POWER4, UltraSPARC III, etc., for comparable power consumption. The Opteron is the closest bet for x86.

Remember, electricity is pennies a KWh.

Although $37 looks small, the savings scales with the company and can amount to thousands of dollars saved. Imagine an 8-way server ($300/year saved) or 32-way server ($1,200/year saved) or an office with 50 workstations ($2,000/year saved). That savings just might replace a broken photocopier or other budget-constrained items.

Power costs aren't something to laugh at, and conservation should be practiced in all aspects of a company (lighting, insulation, etc.). For self-employed people, it can mean an extra week's gasoline, for a large corporation, it can mean not laying someone off. These are real tangible benefits to buying low-consumption devices.

Re:PPC

[ichimunki]

I think you missed his/her point. If the cost of the more energy-efficient processor exceeds the amount of the money saved on the power bills, the company or household is worse off for buying the more efficient model. In the example, the $37 was no match for the $500 extra expense of the system.

Imagine buying a G5 iMac desktop will save me $50/year in electricity bills, but the system costs $200 more than a comparable x86 machine. Then it takes four years for the energy savings to pay for the added equipment expense. Multiplied over 50 workstations, the effect is the same, only the numbers get bigger on both sides of the equation. Just because those 50 machines will save me $2500 annually, doesn't mean they're necessarily worth $10,000 more up front.

However, the energy assumption is a difficult one to make. Energy costs are volatile, generally only increase, and are not an insignificant variable expense for most businesses-- minimizing that expense is not a bad move.