Reply 20 of 23, by 386SX
From my experience I can agree with many saying the Barton 3200+ and the Thunderbird 1400 really requires a 5V strong good quality PSU which specifications are real and possibly dedicated for those cpus. I don't know if nowdays some PSU manufacturer did some serious 5V strong/ripples free model out there, but with the ones I tried (nothing expensive but also some low end Corsair one) the 5V line went really down too much and ended up using some Enermax of those times that really had no problem (if they still works). Also the Athlon cpu I suppose had mostly no power saving logic and from what I can remember even in idle/desktop with a low end vga, it draws from the wall plug 110W the whole computer to goes up depending on the vga and the gpu load. But the cpu load actually didn't stress much more the wattage if I remember correctly. What it requires, it requires it all the time with no variation, this might be also something to consider. Lately I tried a P4 Northwood @ 3Ghz and while it was heavy too on the PSU, in linux it had a kernel module to adjust freqs/voltages and in idle the wattage went down to 80W for the whole computer.
Also the ripple thing for the retro boards it'd be interesting to know which modern cheap psu has been tested to be safe beside the 5V wattage requirement to use with a very old mainboard like an AT one.