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Comparative G5/G4 Tests
rocketjam writes "Barefeats.com has posted test results comparing a 2GHz G5 MP, 1.8GHz G5, 1.6GHz G5 and G4 MP's at 1.4GHz, 1.25GHz and 1GHz. They use Photoshop, Cinebench 2003 and a Bryce 5 render for tests. Bottom line is the G5 2GHz MP has the best bang for your buck, but you might think twice about trading in that dual processor G4 for a solo G5...the G4s hold their own quite well. They also say tests in Panther yielded significant increases in the G5 scores."
A lot of programs are yet to be at all tweaked for the G5s. There are a couple of new processor functions (hardware square root for instance) that may bring big gains. Also, there are old functions from the G4 that slow down the G5. Check out Apple's G5 performance primer. I read that the changes are enough to make the guy who made the mac rc5 engine want to re-write it for the G5 (no simple tweaks). He was hoping to get by with just some minor tinkering, but the chip does require a lot more than that to take advantage of it's potential.
Let me take another example; regarding CineBench.
http://www.postforum.com/forums/read.php?f=6&i=87
In that post, a guy called Richard from the Maxon development labs says this:
This compares to a 1.8ghz G5 score that I've seen of 188. Which means they're aiming to get a fair bit out of optimisation for the chip. Just as a means of further comparison...
http://www.imashination.com/bench.
You'll see the top score these people have recorded is for a dual Xeon 2.4ghz - with a score of 502. If the G5s make it up to over 500, that says a lot about the chip.
Finally, you've also got to include a mention of the compilers. Whilst some optimisation has been made to GCC, the GCC guys rejected a whole heap of improvements for the G5 because they were too platform specific. There's a good thread over at Ars Technica that discusses some pretty big gains when using the IBM XLC compiler. Other Mac-specific compilers should yield some pretty awesome gains too.
So, in summary - take these scores with a grain of salt. They're just the beginning.
-- james
g{The G5 is NOT going to excel at Altivec optimised code, the G4 will remain the Altivec champ until IBM puts the kind of Altivec resources onto the 970 that Moto put onto the 745x series}g
That's not strictly true, the problem is that altivec that's optimal for the 745x chips is worst case for the 970, since best case on the 745x makes heavy use of the vec_dst (prefetch) instruction, which is handled serially on the 970 and hence stalls the Altivec hardware.
also the G5 is a lot less likely to run into bandwidth bottlenecks with altivec code on large datasets.
Why on earth should I choose a G5 over a dual G4?
The G5 is faster.
The G5 accommodates four times the RAM (roughly), and the RAM is considerably faster.
The G5 has AGP 8x.
The G5 has USB 2.0.
The G5 has FireWire 800. (The last generation G4 did, but the generation currently being sold by Apple is next-to-last and so does not.)
The G5 has Airport Extreme. (Ditto.)
The G5 has Bluetooth. (Ditto.)
The G5 has internal serial ATA.
The G5 has digital audio I/O.
The G5 is considerably quieter.
If none of that stuff matters to you, get the G4. If it matters, get the G5. This isn't a clear-cut case of "G5 better than G4 in every way." But neither is it even remotely a case of "no reason to buy G5."
". The code is optimized for the mac. My friends P4 2.8ghz is only a little faster than my G4 733. Apple took advantage of this for years and had test results based on photoshop."
/somewhat/ different than those for prior PowerPC processors and the optimizations that took place for the G4 (such as using vec_dst in the AltiVec optimized portions of the code) actually work against the G5.
:-)
Your working with outdated information--by about 7 years.
The code is optimized for both platforms very heavily. A large portion of Photoshop's userbase is on Wintel machines and they were also paid (by Intel) awhile back to optimize their filters for Intel processors. Presumably they care about performance and keep both versions highly optimized. Saying that it is "more highly" optimized for the Mac is a fallacy--it hasn't even had more time to become optimized for the Mac, due to processor changes. The optimizations for the G3 and G4 are
I also heard a rumor, though I am not sure that it is true, that Photoshop would offload its interface to the graphics card for display on its own and that, with the introduction of QE, Photoshop was effectively rendering its display elements twice. This may be completely unsubstantiated though
While in general your point is good--that apps which are highly optimized for one platform are not necessarily highly optimized for another--Photoshop is a bad example.
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"The G5 is NOT going to excel at Altivec optimised code, the G4 will remain the Altivec champ until IBM puts the kind of Altivec resources onto the 970 that Moto put onto the 745x series. "
/bandwidth limited/. The architecture that the G5 is based on is radically faster when it comes to things like loading from main memory or making optimal use of both processors.
Another poster has already mentioned the execution sterilization that occurs thanks to optimizations that worked quite well in the G4 (vec_dst et al), but there is another point on this issue that needs to be mentioned.
Even if the G5 performs slightly slower than the G4e with AltiVec enhanced code on an individual, it has the potential to be much much faster overall simply due to the architecture. One of the main problems with AltiVec on the G4e currently is that many of the apps that take advantage of it are
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