G5 vs Opteron, Finally

metfoo writes "It's been months since the G5 and Opterons have been available for purchase. When the G5 systems were first released, many Mac bashers and AMD nuts discredited the G5's performance. They always ended their comments with 'Wait until its compared to an Opteron, then we'll talk.' Well, it's finally time to talk. Barefeats has posted an article comparing the two systems. The G5 line was compared to a Dual 2GHz Opteron and the results are impressive. In gaming, the Opteron system proved to be superior, which is partly due to the superior 9800XT over the base Radeon 9800. The G5 spanks the Opteron in many of the non-gaming tests, except for the Photoshop tests."

Comments

Re:Except

[DiscoOnTheSide]

same could be said for the G5, as OS X is not fully 64-bit yet, and neither are many of the programs (with the exception of a few high-level apps, like Photoshop, etc)

Re:Except

[andrewl6097]

The key difference is that the opteron is /faster/ in 64-bit mode. There are more registers. The same is not true of a G5. OSX doesn't "break up" instructions - instructions are instructions. OSes don't interpret each one. 32-bit windows on opteron just uses 32-bit instructions, just like 32-bit darwin on a G5. Photoshop is not a 64-bit app in the case of OS X IIRC - it uses a 64-bit math library as its G5 optimization. This is fine and works. As I mentioned in another post, darwin can't run "64-bit apps" yet, because there are no 64-bit interfaces to system calls (think about it - if the kernel expects a 32-bit FILE * and you send it a 64-bit one, you're going to have trouble doing I/O). I think I missed something with what you said there. The main 64-bit part of darwin is the math library since they can throw some 64-bit ASM in there plus code to convert back-and-forth to the 32-bit bindings.

Re:Except

[mattjb0010]

Are the moderators on crack? That's not informative, it's wrong!

The only "piece" of OSX that is 64 bit is the memory access - to allow a G5 to use up to 8 GB of ram.

No, the math libraries and kernel support 64 bit goodness too. While the G5 chip is fully 64 bit, OSX is taking each 64 bit instruction (from 64 bit apps like Photoshop, for example) and breaking it into two 32 bit instructions which it sends one after the other to the CPU.

No, it runs as a single 64 bit instruction through the chip!IBM is working to provide Apple with a much optimized PPC970 compiler tailored for the G5 - this is expected to give a large performance gain for this platform.

This I agree with, in fact it should be pointed out that the compiler is available now as a beta on IBM's web site.

Top500.org

[RedWingsSuck]

On the latest Top500 list Virginia Tech's Mac cluster is number 3 with 2200 2GHz G5 processors, and Los Alamos National Laboratorys machine, with 2816 2 GHz Opteron processors is number 5.. I didn't look at the topology, or connection medium, but I am certain that the Mac cluster was cheaper, and is faster running the SAME benchmarks...

Re:Top500.org

[Hoser McMoose]

Yup, the PPC 970 (G5) is quite fast at running Linpack, particularly in comparison to x86 chips. The main reason for this is that Linpack is basically just a bunch of floating point adds and multiplies, and the PPC 970 has this nifty instruction that does a floating point multiple and add all in one. On x86 this requires two separate instructions.

Some scientific computing does closely resemble Linpack's workload. Basically any time you're dealing with matricies you are almost always going to be doing lots of FP mult-adds. However, this is a VERY narrow benchmark of CPU performance.

A much better benchmark of raw CPU power is SPEC CPU2000 (though the compiler and memory subsystem play a major role here). Unfortunately Apple has chosen not to grace Spec with it's precense. So far it's only numbers released have been from the Veritest results which "proved" that the G5 was faster than a Pentium4. These results were rather unimpressive and SIGNIFICANTLY slower than the results for Opteron and P4 systems.

All benchmarks have their limitations, Linpack (used by Top500) just tends to be more limited than most. Rumor has it that a new set of high-performance computing benchmarks is in the works to replace plain old Linpack.

Re:Price?

[fearx]

I've read this sort of argument before, and what it comes down to is the difference in price between a comsumer system (G5) and a pro workstation (dual Opterons are not for the avergae consumer). The manufacturers making dual Opteron systems provide very heavy support - because their market (Engineering, 3d modeling, rendering) demands it. You pay for said support. The G5, however, comes with typical Apple support - which, while very nice, is not at the same level.

Actually, the G5 is Apples Pro Line. Their consumer line consists of the iBook, iMac, and eMac. Their Pro line consists of the PoweBook and Power Mac. Maybe the naming gives it away too... POWER Mac, POWER Book.