Garrett W wrote on 2020-04-25, 19:01:
I seem to remember someone saying that the motherboards that have the 4pin P4 plug are not entirely safe from this issue either and you still need a powerful 5V line. Has anybody ever looked into that?
OP, are you running the original Thoroughbred 2800+ or a Barton model? Phil's Computer Lab tested a couple of PSUs and Duron/Athlon processors some years back and found that even a lowly Corsair VS450 can handle Durons all the way up to ~57W TDP, although I'm not sure if those numbers can be trusted (not to mention TDP is weird).
I did. Tested with three nforce 2 motherboards (Abit AN7, Asrock K7NF2 and a Gigabyte Ga-7N400) that have a 4 pin 12v CPU power connector. Using a modern Seasonic Core GC, 80+ Gold, 650W witch boasts 20A on the 5v rail I encoutered instability running a 3200+ (2.33GHz FSB 333 version) and a Geforce FX 5900 Ultra .
Switching to a much older Mushkin XP-650AP (circa 2007 I think, no efficiency certification but a rock solid PSU) that sports a 30A 5v rail made the system stable.
I ran the PC like that for a while, then decided to run a couple more hard disks in it, and the problems came back. Not as severe as before, but the system will sometimes lock up in demanding games after it's been running for more then 60 minutes. I also noticed that under windows 98, even with 512MB of ram, the PC will hang in 3dmark 2001 in the first half of the test suite, something that does not occur under windows XP. This happenes with all 3 motherboards. Using the 650w seasonic PSU, the system will hang after loading the taskbar with all motherboars except for the abit AN7.
After that, I decided to go nuts and tested the system again using my Corsair HX 1200 platinum, witch according to it's specs boasts a 30A 5v rail. It was perfectly stable under XP and 98, using all motherboards - so at this point I was thinking "what gives?"
I got a hold of a clamp amp-meter, and decided to measure the amount of power going trough the 12v lines of the 4 pin CPU aux connector. Under full load, in windows 98, using the Abit AN7 board, the CPU uses 4 to 6 amps off the 12v rail witch is not quite right, since the 3200+ has a power rating of 60.4 / 76.8 Watt (or at least this is what CPU world claims). Then I put the amp-meter on the 5v lines running to the ATX connector, and noticed it was drawing over 15 amps from that line as well.
I still don't understand what exactly is happening, but it seems the CPU either uses power off both the 5v and the 12v rails, or the 4 pin CPU connector only feeds the PCI and AGP slots on the motherboard. Even so, considering the power draw I measured, any modern PSU with a 20A 5v rail should be enough for a 3200+ right? But in practice that's not the case...
Perhaps the issue is how "clean" the 5v rail is? Personally, I'm stumped.