Both install fine and show up in device manager. Same bios on each card....both show up in nvidia control panel, and it even allows me to select one of them for physics but no sli option. I'm dumb thanks.
Btw using latest whql driver xp x86
out of 1.23 1.24 1.25 and 1.28 chips
1.23 = 6.73ghz
1.24 = 6.65ghz
1.25 = 6.45ghz
1.28 = 6.37ghz
Seems like some batches just stop scaling with volts earlier. the 1.23 6.73ghz chip can do 6.58 at 1.68v but then eats volts up to 6.73ghz