Need help with 200fsb stability - A1 (C1) stepping

I am having problems getting stability at 200 fsb synch. Currently my board is stable at 200x7.5. It will run prime 95 fine for at least an hour. It was stable before at 180x11.5=2079mhz @1.675v I tried to run at 200x10 @1.675v but it has problems with prime 95 giving me an error right away. It also sometimes has problems with 3dmark 2001 SE or some games. Is it possible that I need considerable more voltage to do 200 fsb instead of 180fsb at the same processor speed? Here are my specs:
1700+ B version week 51
8RDA+ 1.1 A1/C1 stepping
Gf4 4200
SLK800
Antec (Cheiftec case)
Kingston hyperx 3500 @ 2.77v

I tested the memory at 200fsb with memtest86 v3 and it is fine.

I am currently running stable at 7.5x200.

What BIOS version are you running?

3/05/03 I am at 200x9.5 @1.75v now and good so far................