Slow Folding on G4

How is the Folding performance on the dual-G4 machines? I found that an Athlon XP PC is twice as fast as a fancy Apple system with a G4 of the same MHz rating as the Athlon. Aren't Macs supposed to be twice as fast as x86 systems?
For example, the Athlon can process one frame of p692_L939_K12M_int in about 10 minutes, while the dual-G4 takes over 20 minutes. Is there something wrong with the Mac or the Folding client, or is a 2-year-old Athlon PC really a faster system than a new PowerMac G4?

Can the Folding application request Gromacs units? Most of the units that I've been getting lately are p638 and p692. It's silly to be processing this data on a PowerMac when a low-end PC can do the work in half the time and the G4 could be doing something else. I'm doing a p692 unit now and it took so long for a frame to be processed this morning that the PowerMac went to Sleep. I have to select Display Protein in the application to keep the system active.

I might just stop Folding on the Mac if this slow processing continues. It's not worth the cost of the CPU time. There are other things that the G4s could be doing other than struggling with non-optimized Folding units.

There are other distributed computing projects available and I have my own work to do. Folding gets an allotment of the available CPU time on a set schedule depending on the work load each week. If it takes the PowerMac more than a week to complete a work unit normally, and more than two weeks when I need more CPU time for other work, it's not worth keeping it running. The Athlon can do a large work unit in under five days. I've joined the MacRumors Folding team. Most of the points that I've posted have come from an Athlon PC. The Athlon has done two units and is almost done with the third one while the PowerMac is only halfway through the second one, and the Mac has been running almost every day with no other CPU-intensive tasks while the Athlon system has had less time for Folding. If I got an Athlon system running full-time, maybe even with a new AMD 64-bit CPU, it would make the G4 look like an old Pentium at Folding performance. This would be a bad thing to show at a keynote. I wanted to show people the Athlon and the G4 doing Folding so that they could see how the Mac is twice as fast as the x86 PC, like at the Apple keynotes, but it's really the old Athlon that's twice as fast. I like the PowerMac performance overall, but Folding just isn't what it likes to do.

The p692 unit that was running has just been finished. A large download occurred and it's the Gromacs Core v.1.54.

The Folding client says:
"Extra AltiVec boost OK."