I bought a Sempron 2800+ CPU yesterday (Tbred core, FSB 166). When i started up my PC with it, it was recognised as an Athlon 2400+, but that is not the problem, since it worked at 2000Mhz (as supposed). The problem starts here: bios reported a default voltage of 1.775. I know that this cpu is supposed to work at 1.6 so i lowered the voltage to 1.6. My system became far from stable. Prime95 didn't even start the stress test, saying "FATAL ERROR: Rounding was 0.4999988412, expected less than 0.4", not to mention 3dmark 2001 wich had numerous lockups. So i have set the voltage back to default (1.775) from Bios wich is actually 1.8v. Now suddenly Prime95 ran fine for 30minutes with 0 errors, 0 warnings, and i have ran 3dmark once with no problems. Now comes my question: Is the board reporting the voltage incorrectly? It is not even supposed to support Sempron...

do you have newest bios flashed on the mobo?

edit: k5a23916.bin

I tryed the newest bios but the situation is the same. I flashed back the original bios because using that i get 2000.x Mhz versus 1988 with the newest bios. Epox has a CPU support chart that does not mention Sempron to be supported on 8k5a2.    

I have the same phenomenon with 8k5a3+ and a Barton 2500+ CPU. The default Vcore is 1.650V. But I set the Vcore at 1.575. The USDM Software (Epox Diagnose-Prog) shows me 1.632V. I don't know if the board reports the voltage correctly, but I know it's stable :)

Yeah, this is also my suggestion I think the board doesn't report the Vcore correctly. If the system runs stable @ 1.775 I think it is ok.

My thought exactly. At 1.775 the CPU is perfectly stable so i'm just going to leave it like this.