Quite a few people including me have problems with high v core voltages and high FSBs at the same time. Well here's something to play with. I/O voltage. Yep, the now neglected voltage seems to be back. I've problems getting 238Mhz FSB to run stably at voltages over 2.15v and problems booting into windows stably at 240 Mhz FSB at 2.125v. Well I have a chanelwell powersupply that has tweakable potmeters inside for 3.3v rail and 5v/12v rail. Well I've had my 3.3v (I/O) set at 3.36v or so in the past. Well I decided to play with it and set it to 3.58v maxing at 3.60v. Thats the max I can set it before my power supply's over-voltage protection cuts off the power.
Well, upping the 3.3v rail has another effect other than upping the I/O voltage. Dimm voltage moves up a bit too.
Anyways I decided to give these high FSB/high voltage problem another try. So I went into windows at 238 FSB at 2.15v. And then I fired up Prime 95 expecting it to turn yellow in a while. Waited for a few minutes. Still red? Hmmm..... and then it just went on running prime 95 without failing when in the past it would fail quite quickly!
Ok ok, maybe its the dimm voltage that went up a little bit. So I rebooted and lowered the dimm voltage one notch. Went into windows and prime 95 again. And it was doing it like just now, no failures when it was impossible in the past! So ok, I was pretty excited. So I turned down the PC, tweaked the 3.3v rail down to 3.36v or so and tried prime 95 again. This time, it failed in just a short time.
So to double confirm, I loaded her up at 240 Mhz FSB 2.125v, 3.36v I/O. into windows and this windows error and shutting down timer comes up like usual. Turned her off and uped the I/O to around 3.56-3.58v. Booted straight into windows without any annoying countdown to shutdown and still running now, although prime 95 does fail ATM, ram timings or maybe not, but the fact is the I/O voltage does play a significant part. And I would expect it to also help FSB overclocking, maybe not as much as VDD but there should be some effect I think. Now for more stability and more effect, I think I would want to up it to 3.8 to 3.9v if I could. But this is impossible for me until I mod the board itself. I'm gonna try a 420 watt chanelwell to see if I can get over 3.58v. Anyone know which is the I/O voltage regulator on the NF7?