Try removing and reinserting your RAM. If you have more than a pair of SIMMs installed, try it with just one pair installed, and if the problem persists, try the other pair instead. Maybe inspect the RAM contacts and the RAM slots for any corrosion?

Does the board work with an original listed supported CPU (like P-133, P-200MMX) ?

Thanks for your replies!

MoBo works fine and 100% stable with P133 and P200MMX. Both here on my table. Its mysterious. Just with the K6-III the MoBo has a problem.

@Repo Man11
I'll check, but it's strange that the other CPUs are running fine.

Any other ideas 🙁 Can the power supply really be ruled out as the cause of the problem?

I took a closer look at the USB port. Normally a USB hub is plugged in to the USB header, which is powered externally. If I leave the hub plugged in and remove the external power supply, the reboot is even faster when the BIOS is first displayed. When I leave the peripherals connected directly to the header without the hub, the system restarts after BIOS boot as before. So it seems the 5V supply has an impact to the system.

Best regards and thx,
JF

Repo Man11 wrote on 2023-11-19, 04:15:

Try removing and reinserting your RAM. If you have more than a pair of SIMMs installed, try it with just one pair installed, and if the problem persists, try the other pair instead. Maybe inspect the RAM contacts and the RAM slots for any corrosion?

I have checked the RAM and have additionally decreased timing to 70ns instead 60ns. No effect.

Best regards,
JF

"I have unplugged all cards and stuff except the graphics card and found out that the system boots when I have also unplugged my USB header with keyboard and mouse. (?)"

Have you tried using a PS/2 mouse and keyboard? Assuming that you will be using Win9x, a PS/2 mouse is a good idea anyway since it also works during setup, and when you boot into Safe Mode.

JF_Sebastian wrote on 2023-11-19, 03:55:

Is it possible that my power supply seems to have not enough power on 5V rail for the K6? My power supply is an old seasonic with 200W which should supply 20A @5v (says the type plate 😁)

This is easy to check. Install only the minimum hardware for the most stable configuration, turn the system on, and probe the 5V supply rail for voltage with a voltage meter. Turn off, add a card and turn on and probe again and repeat. This doesn't check for ripple, but anything too low you'll see. With ripple, it's better to check with a scope, but you should see more random instability in devices connected.

Repo Man11 wrote on 2023-11-19, 15:02:

"I have unplugged all cards and stuff except the graphics card and found out that the system boots when I have also unplugged my USB header with keyboard and mouse. (?)"

Have you tried using a PS/2 mouse and keyboard? Assuming that you will be using Win9x, a PS/2 mouse is a good idea anyway since it also works during setup, and when you boot into Safe Mode.

That's true and with PS/2 and AT keyboard the system boots much more often. So far I have connected keyboard and mouse via the original ASUS USB header and it has worked fine with all other CPUs - the MoBo even has USB support in the BIOS. This is great and I can use a USB switcher to share keyboard and mouse from my everyday PC and the retro build 😉 But even with PS/2 and AT keyboard the system is unstable.

In the next few days I will receive a TAGAN TG480-U01 power supply from a friend. This can supply more than enough current on the 5V and also has a minus 5V rail. I think this is a good candidate to check if the power supply is the root of all the trouble. I hope so! 😁

Best regards and have a successful start to the week!
JF

the3dfxdude wrote on 2023-11-19, 16:07:

JF_Sebastian wrote on 2023-11-19, 03:55:

Is it possible that my power supply seems to have not enough power on 5V rail for the K6? My power supply is an old seasonic with 200W which should supply 20A @5v (says the type plate 😁)

This is easy to check. Install only the minimum hardware for the most stable configuration, turn the system on, and probe the 5V supply rail for voltage with a voltage meter. Turn off, add a card and turn on and probe again and repeat. This doesn't check for ripple, but anything too low you'll see. With ripple, it's better to check with a scope, but you should see more random instability in devices connected.

Thank you for your good suggestion. Thanks to my friend, I prefer the lazy solution with a working power supply. 😁