No more mysteries: Apple's G5 versus x86, Mac OS X versus Linux
by Johan De Gelas on June 3, 2005 7:48 AM EST- Posted in
- Mac
Workstation, yes; Server, no.
The G5 is a gigantic improvement over the previous CPU in the PowerMac, the G4e. The G5 is one of the most superscalar CPUs ever, and has all the characteristics that could give Apple the edge, especially now that the clock speed race between AMD and Intel is over. However, there is still a lot of work to be done.First of all, the G5 needs a lower latency access to the memory because right now, the integer performance of the G5 leaves a lot to be desired. The Opteron and Xeon have a better integer engine, and especially the Pentium 4/Xeon has a better Branch predictor too. The Opteron's memory subsystem runs circles around the G5's.
Secondly, it is clear that the G5 FP performance, despite its access to 32 architectural registers, needs good optimisation. Only one of our flops tests was " Altivectorized", which means that the GCC compiler needs to improve quite a bit before it can turn those many open source programs into super fast applications on the Mac. In contrast, the Intel compiler can vectorize all 8 tests.
Altivec or the velocity engine can make the G5 shine in workstation applications. A good example is Lightwave where the G5 takes on the best x86 competition in some situations, and remains behind in others.
The future looks promising in the workstation market for Apple, as the G5 has a lot of unused potential and the increasing market share of the Power Mac should tempt developers to put a little more effort in Mac optimisation.
The server performance of the Apple platform is, however, catastrophic. When we asked Apple for a reaction, they told us that some database vendors, Sybase and Oracle, have found a way around the threading problems. We'll try Sybase later, but frankly, we are very sceptical. The whole "multi-threaded Mach microkernel trapped inside a monolithic FreeBSD cocoon with several threading wrappers and coarse-grained threading access to the kernel", with a "backwards compatibility" millstone around its neck sounds like a bad fusion recipe for performance.
Workstation apps will hardly mind, but the performance of server applications depends greatly on the threading, signalling and locking engine. I am no operating system expert, but with the data that we have today, I think that a PowerPC optimised Linux such as Yellow Dog is a better idea for the Xserve than Mac OS X server.
References
Threading on OS Xhttp://developer.apple.com/technotes/tn/tn2028.html
Basics OS X
http://developer.apple.com/documentation/macosx/index.html
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michael2k - Friday, June 3, 2005 - link
Well, it shouts to stay away from the XServe unless you happen to have vectorizable code that you have the resources to properly vectorize!erwos - Friday, June 3, 2005 - link
Excellent comparison of the platforms, although I actually wish they would have spent more time analyzing the graphs.Like the others, I would have liked to see a G5 / Linux benchmark (now that FC4 has a PPC version, you could run a fairly reasonable one), but I do admit it's not a very popular option compared to x86. My curiosity is whether MacOS X is the problem, or whether it's some sort of issue with the CPU itself. Seems unlikely the G5 would have such a fundamental flaw, but it does shout to stay the hell away from the Xserve until these issues are resolved.
-Erwos
Thresher - Friday, June 3, 2005 - link
As the owner of intel, AMD, and Mac based computers, I have to say this is one of the best and most thorough comparisons I've seen.You did an excellent job of isolating CPU and OS performance.
That being said, if performance were the only indicator, there is no doubt in my mind that AMD would be ruling the roost. However, personal preferences come into play to a great deal. Businesses like the reputation behind intel. I prefer the usability of Mac OS X. People have strong feelings about Microsoft that may color their decisions.
When it comes down to it, performance is important, but not the only reason people buy what they buy. I would say more often than not, the decision is made with only a modicum of logic.
Cruise51 - Friday, June 3, 2005 - link
I'd be interested in seeing how it performs on yellowdog aswell.IntelUser2000 - Friday, June 3, 2005 - link
People, in case some of you misunderstand, the 10.8GB/sec Full Duplex bus means that its two 32-bit 1350MHz bus, rather than one 64-bit bus in the PCs. Its not, 10.8GB/sec x 2 =21.6GB/sec bus, its 10.8GB/sec bus(or more correctly stated 5.4GB/sec x 2). Plus, it says in Apple site that it has TWO(yes two!!!) of the 10.8GB/sec buses, per CPU.Summary: Per CPU=10.8GB/sec
Per Dual Processor System=21.6GB/sec
Johan, about the AMD TDP number, they never state that its max power, they say its maximum power achievable under most circumstances, its not absolute max power.
JohanAnandtech - Friday, June 3, 2005 - link
Porkster: It is a little geekisch Unix joke. Where is your geekish you man spirit?Wessonality: Our next project if we can keep the G5 long enough in the labs.
Ailleur2: indeed, I agree. The G5 is a potent CPU with a lot of potential. Just give it a bigger L2 and a better memory subsystem. This is an architecture that could last very long by applying a few tweaks, like the P6.
Methodical: All of the benchmarks are trustworthy, they should be looked upon as a whole to get a good picture, not just pick one. About After affects, I indicate that the G5 does very well here (seen other reports on the web), I just didn't have the software in the lab.
I also warned that this was not about "should I buy an Apple or not?". It is just "if performance is what counts for me, where should I position the G5/Mac os X combiantion compared to x86/Linux/Windows ?".
StuckMojo - Friday, June 3, 2005 - link
hmph. you say it yourself in the last paragraph...how come you didn't try it?
StuckMojo - Friday, June 3, 2005 - link
yes, it seems you've left out a very good method of testing if OSX is the issue: run a powerPC linux distro with the mysql and apache benchmarks and see what happens!i'd be _really_ interested in the results. see if you can update the article with them.
porkster - Friday, June 3, 2005 - link
"Root Me" in Australian slang is the same as "Fxxk Me" in common language. Some people my find a picture in this review offensive.wessonality - Friday, June 3, 2005 - link
What about installing Yellow Dog Linux on the XServe?