Seeing how high the chip will go at POST is always an entertaining, if misleading way of gauging a system’s overclocking potential. To minimise the chance of any memory limitations I temporarily set the Twin X to CAS 2.5, 8 - 4 - 4 timings at 2.8V. This should give it plenty of leeway in the MHz dept, even if you would never want to use a system at these settings.
To begin with I set the V-core to a conservative 1.6V, around 0.075V over stock voltage. I set the Ram ratio to 3:2 (0.75x FSB) and started increasing the FSB. At 273Mhz I hit a wall. Already a whopping 900Mhz over stock, this was rather exciting as temperatures were still in the 40s and we had not even started hiking up the voltage to dangerous levels.
I decided it was time to stop being such a pussy, so I whacked the voltage up to 1.75V (an increase of 0.125V over stock), still not a dangerous amount so long as you have decent cooling. At this point I was able to increase the FSB all the way up to the maximum setting of 300MHz without any signs of problems. However, at this FSB my memory is still only running at 200MHz. That 3:2 ratio is very handy =). A quick BIOS flash to unofficial BIOS version 1.3 (you can't get it off Abit's website yet, but I'll let you have it for free here) removed the 300MHz limitation. [update] Abit now have a version 1.5 beta - grab that here.
At 1.75V I have reached the maximum voltage I'm prepared to go to with a D stepping Pentium on air alone. Back in the old 1.8a days I was happy to pump 1.9V into the chip just with a decent HSF, but these new CPUs don't like high voltage nearly as much. I would say unless you are using a Vapochill or something similar, this should be the maximum voltage you try =). At this voltage I was able to post the chip at 323MHz FSb, for a chip speed of just under 3900Mhz. Vroom!
