Oh, I think some of that advantage comes simply from the fact that the machine was allowed to run at only 640x480. If you setup a P3 733EB and GF3/4 (NV2A is sorta like a NV25), and run 640x480, you could run FarCry PC pretty well. And that would be more than Xbox 1 ever did. The bandwidth and dedicated RAM that the vid card has to itself would probably actually beat up Xbox 1.
Sure the devs can really tweak down to the hardware, but the result depends on how much missed potential there is in the hardware. NV2x was designed as a PC accelerator and I think that means that it was probably pretty well utilized on PC. It's not like a quirky EE+GS.
I used to have a rig sort of like that...
Athlon XP 2200+, 1GB ram, Geforce 3, and it could run any games that were on both xbox and pc (like halo and doom 3) at about the same fps but at 800x600 instead of the 640x480 limit. (though xbox probably had the power to spare to run at 800x600)
Of course, xbox exclusives likely would have outdone it considering that both halo and especially doom 3 just treated the xbox as if it was a low spec pc. (well, high spec when halo came out)
Oh, and Farcry on Xbox looked pretty good.
I agree, although you also have to consider the overhead of the OS/API and background processes aswell. Accounting for this then you should probably be comparing to something like a 1200Mhz Athlon with 256MB of system RAM.
That seems a bit extreme on the cpu side, but perhaps a bit low on the ram side. Windows and its apis don't seem to eat into that much cpu time, but eat so much into ram. I'd say you'd probably wanna up to 512MB, and accounting for the higher IPC, get away with like an 800mhz athlon.