I have a v3 that I'm having this terrible problem with.
I'm using a k6-III 450 1.8v spec running at 1.8, 66mhz * 4.5, ~50 degrees C "system temp" according to the BIOS, ~35 degrees C CPU temp.
I have a big CPU fan, a strip of aluminum cooling down the hot q16 transistor, the cooling resistor installed, Badflash's in-line power supply resistor, Badflash's latest BIOS, a 6 gig toshiba hard disk, and an op-amp board from an old Toshiba laptop docking station epoxied in there.
The cooling resistor is attached with very short large guage wire to q16, and physically presses against the side of the CPU heatsink (normal socket7-type fan/heatsink combo)
After about 2 minutes of running Windows 98SE, the system just mysteriously reboots.
At first, I figured it had to be a heat problem - so I installed a bigger fan and a bigger aluminum cooling strip (it's a bit of aluminum RF shielding, cut in a square with a strip off the side that runs between the cpu/heatsink to the hot transistor with heatsink goo slathered on it). No go. exact same problem.
I've tried setting the Vcore to 1.7, 1.8, 1.9.. No go. I could try higher, but not sure this would do any good.
If I set the multiplier to 3, it works. But I'd like to have at least 4.5*66. Higher bus speeds do not seem to work, the system never boots at all.
I've scoured the board for hints, but I'm just out of ideas for this one. I'd like to replace q16 with something a little beefier that I could attach a heatsink to in a normal way, but everything I've read here seems to indicate that's not a good idea/necessary.
Please, any ideas are welcome!