I had a little "learning experience" which may benefit others running PPC Macs. (SETI, Einstein, SIMAP, and WCG are major projects that still support Mac PPC work.) I am using OSX 10.4 on a G5. This should still affect G4's, but I'm not sure if it is in OSX 10.5 or 10.3. In "System Preferences", under "Energy Saver", the second screen "Options", there is an option for "Processor Performance".

It seems that Processor Performance works a little differently than Speed Step on the Intel side. It seems that the default setting of "Automatic" actually disables the factory-set overclocking. On my Mac, when I set it to "Maximum" and re-ran the CPU benchmarks, the computing power increased by about x2.4. Suddenly my G5 is as powerful as a G5 should be and is close to my AMD's.

Yes, I know the BOINC meme is "Overclocking is bad", and I'm not arguing with that. However, this is factory set. Most processors these days are overclocked at the factory, and run at the same accuracy as if it is disabled. Increases in refinement quality allowed processors to be overclocked by as much as x2.5 with no performance issues. About five years ago, the reason speeds kept increasing and heat output kept increasing was that processors were not truly getting faster, but more tolerant of (factory-set) overclocking. About 4-3 years ago, processors were increasing in transistor density, overclocking was turned down, and so the market saw processors running slower and producing less heat but still maintaining data throughput. Processors were working smarter and not just pushed faster.

Anyway, I had my G5 since 2002, and only now discovered this. It's a bit frustrating and embarrassing. I hope there are a few other Mac users who can get a performance boost from this, but with the warning power consumption will increase, and make sure the cooling fans are clean and working. The processor will burn hotter, so don't do this on a Mac that's rattling along on its last leg.

I don't have exact numbers, but as a comparison, the CPU benchmarks previously tested the floating point at about 740 MIPS, and now are testing at about 1850 MIPS. The Mac is a G5 2.3GHz. My Phenome X3 is 1650 floating point MIPS, while my Athlon 64 is a bit higher.

I have a PowerMac G5 Dual 1.8 (2004) running 10.5.8 with 2GB RAM, and changing the "Processor Performance" setting made no difference in my BOINC performance. An average of three recent benchmarks is 1446 floating point/2917 integer MIPS per CPU. Perhaps what you are experiencing is a limitation or issue with 10.4?

Another factor that will limit G5 performance, is that I'm not aware of any projects that have a 64-bit PPC application. Typically there is just one 32-bit app for G4/G5 series processors; I don't know of any projects that have apps that still run on G3s.