8RDA+ VDIMM not working above 2.62 volts?

Pardon me if this is a newbie question, but I just set up a late board (4-21-03 manufacture date). It has the March 5th BIOS and the C1 northbridge. If I set VDIMM to 2.77 or 2.90 I still get 2.62 in the BIOS and diagnostic utility. Is the VDIMM adjustment in the BIOS working?

I am running a single 512 MB stick of Corsair XMS3500 C2 in the DIMM1 slot. I can do 205 fsb at 2-2-2-5 at 2.62 volts, which is pretty good, but I could hit 228-230 on an NF7-S board with the same stick, where I could go up to 2.96 VDIMM.

So are the VDIMM settings on the 8RDA+ bogus? Am I supposed to remove a jumper on the board or something?

try a different bios thats about the only way to fix the vdimm/vcore issues. esp since corsair warranties their ram until 3.0v...it should be fine at that.

Thanks for your suggestion RangerJoe, I guess that's the only thing I can try. I am very surprised as Epox is known for offering radical VDIMM on their Pentium4 boards and it doesn't even work on this Athlon board.

I tried relaxing settings all the way to 2.5-3-3-6 and I still can't get over 205 fsb. I do know the XMS3500 C2s need voltage to do spectacular things. On a Pentium4 rig, I've taken the same stick to DDR472+ at 3.0 volts.

And that's DDR472+ at 2-2-2-5. I was CPU limited and reckon it will do DDR485+, 2-2-2-5 at maybe 3.2 volts.

I solved the problem by flashing to the latest May 2003 BIOS. Now the VDIMM is adjustable in the BIOS. I also had to move my 512 MB stick of XMS3500 C2 to the DIMM slot nearest the CPU. Result:

VDIMM = 2.62 allows 200-208 fsb
VDIMM = 2.77 allows 210-214 fsb
VDIMM = 2.90 allows 215-219 fsb

All settings are 2-2-2-5! I cannot get above 219 fsb as the 1.56 VCC is too limiting. On an Abit NF7-S I can hit 228-230 fsb because I can use 1.7 VCC. Still, I am pretty happy at 219 x 11.0 or 2409 mhz, 2-2-2-5. The XP2100+ I have needs 1.88 VCORE to be stable here, but everything in 3D passes as well as SuperPI. Pretty solid rig. I got about the same overclock on this CPU in the Abit board, where it needed a bit more VCORE (1.90) to hit the same 2409 mhz.

Funny thing with this board and my Corsair is it won't boot at all with certain dividers like 10.0 or 10.5. The Abit board had no issues there.

I feel the Epox board is quicker seat-of-the-pants, though. But I have to test the NF7-S board again as I did not have DMA enabled on the HD.

To add my quick OT two cents, I think Corsair's vdimm limit is 2.8, not 3.0

~THT