I have an AT system with a PCChips M520 motherboard that I upgraded to a K6-3+ 450 that suddenly began giving me strange issues (failing to POST consistently, crashing when running 3D 99/2000) , and I finally realized that the antique AT power supply was failing. It had been working fine with the original CPU and video card, but adding (relatively) power hungry hardware was more that it could handle; replacing the power supply resolved the issues I was having. The TDP of the K6-2 400 is 22.7 watts, while the 200 MMX is 15.7 which shouldn't be an issue, but it might be just enough if the PSU is on the edge.

Repo Man11 wrote on 2025-03-07, 13:31:

I have an AT system with a PCChips M520 motherboard that I upgraded to a K6-3+ 450 that suddenly began giving me strange issues (failing to POST consistently, crashing when running 3D 99/2000) , and I finally realized that the antique AT power supply was failing. It had been working fine with the original CPU and video card, but adding (relatively) power hungry hardware was more that it could handle; replacing the power supply resolved the issues I was having. The TDP of the K6-2 400 is 22.7 watts, while the 200 MMX is 15.7 which shouldn't be an issue, but it might be just enough if the PSU is on the edge.

I'm using a high quality, modern PSU. So it shouldn't be that... and the USB ports/keyboard work perfectly when it is booted into Windows 98

Lostdotfish wrote on 2025-03-07, 13:46:

Repo Man11 wrote on 2025-03-07, 13:31:

I have an AT system with a PCChips M520 motherboard that I upgraded to a K6-3+ 450 that suddenly began giving me strange issues (failing to POST consistently, crashing when running 3D 99/2000) , and I finally realized that the antique AT power supply was failing. It had been working fine with the original CPU and video card, but adding (relatively) power hungry hardware was more that it could handle; replacing the power supply resolved the issues I was having. The TDP of the K6-2 400 is 22.7 watts, while the 200 MMX is 15.7 which shouldn't be an issue, but it might be just enough if the PSU is on the edge.

I'm using a high quality, modern PSU. So it shouldn't be that... and the USB ports/keyboard work perfectly when it is booted into Windows 98

In that case I've got nuthin, so have a bump.

Not sure exactly what it was but it's working now...

I did a few things all at the same time - so need to retrace my steps and see what the route cause was...

Main thing I changed was from 2x32MB SIMMS to 1x64MB SDRAM but I also changed some resource settings around the parallel and serial ports

Lostdotfish wrote on 2025-03-07, 16:07:

Not sure exactly what it was but it's working now...

I did a few things all at the same time - so need to retrace my steps and see what the route cause was...

Main thing I changed was from 2x32MB SIMMS to 1x64MB SDRAM but I also changed some resource settings around the parallel and serial ports

and now it's happening again - so weird

Did your motherboard officialy support K6-2? I had the same issue with restart loop when i installed k6-2 on my TX system (bios from 1997+ bios pather). Bios upgrade fix it.

elmatero wrote on 2025-03-08, 16:29:

Did your motherboard officialy support K6-2? I had the same issue with restart loop when i installed k6-2 on my TX system (bios from 1997+ bios pather). Bios upgrade fix it.

Yes, and I've updated to the latest BIOS and a patched BIOS that extends K6 support.

It is literally the USB legacy support that does it - enabled + k6 = boot loop - disabled + k6 is fine
Enabled + Pentium MMX = absolutely fine - I even made sure leave everything else configured the same - same base frequency, same multi etc