Micronics board: How is the RTC doing? When this fails, you can get these symptoms. Also try a slower bus speed like 20 or 25 MHz if possible.

Soyo board: This board has a 5V - 3V voltage regulator. I don't know how it behaves when a Overdrive CPU is installed. Can you try a non-Overdrive cpu? See if the voltage regulator and CPU gets warm, if not; dead voltage regulator? Set JP24 accordingly.

When using the Overdrive, set the jumper to 5V. The Overdrive will do the voltage conversion.

These two things are common issues with 486 systems. I'm mentioning these based on what you are saying about the Micronics board, but one these issues can be affecting either.

1) Most 486 systems have a turbo function. Make sure you are engaging turbo mode
2) Most 486 systems cannot accept EDO 72pin memory. Make sure you try known Fast Page memory in the board.

PD2JK wrote on 2025-06-13, 13:10:

Micronics board: How is the RTC doing? When this fails, you can get these symptoms. Also try a slower bus speed like 20 or 25 MHz if possible.

Soyo board: This board has a 5V - 3V voltage regulator. I don't know how it behaves when an Overdrive CPU is installed. Can you try a non-Overdrive cpu? See if the voltage regulator and CPU gets warm, if not; dead voltage regulator? Set JP24 accordingly. HOWEVER, I should also report that the CPU was being reported as 50Mhz on this board even wit the correct jumper settings which is odd

When using the Overdrive, set the jumper to 5V. The Overdrive will do the voltage conversion.

Thank you for the reply. I have a fresh external battery installed in the Micronics board. It's a 3cell lithium battery pack to replace the old alkaline one. I'll look and see if I can try the lower bus speed. I've never seen a screen refresh problem like this in BIOS before. I can confirm that the battery is working to the extent that the BIOS settings get saved on exit.

In the Soyo I do have a DX266 I can try when I get home. I do have the jumper 24 set to 5v

the3dfxdude wrote on 2025-06-13, 13:22:

These two things are common issues with 486 systems. I'm mentioning these based on what you are saying about the Micronics board, but one these issues can be affecting either.

1) Most 486 systems have a turbo function. Make sure you are engaging turbo mode
2) Most 486 systems cannot accept EDO 72pin memory. Make sure you try known Fast Page memory in the board.

I will for sure have to test the turbo switch on the Micronics board. I know the cable for the switch is in the proper orientation. Also, the RAM that I purchased is FPM and is listed as 16MB 4Mx36 FPM Memory PARITY 60NS SIMM 72-PIN 5V

I got the Micronics board situated but it has a blue overdrive socket as the only socket so my CPU would never run above 50mhz in it.

The Soyo keeps giving me memory errors (long beep) now. I finally had it working minus the IO card not doing as it should which I guess was leading to the black screen after initial post. I figured out that one of the 72pin slots was causing errors because it stopped freezing with just one slot used. I notice the slot seemed just a tad loose so I tried to reflow the solder connection on the bottom and added some fresh solder but didn’t help and after booting a few times I’m now just getting a memory errors al together.

I found some corrosion on the cmos clear jumpers and cleaned the area with vinegar. It’s odd since it uses a coin cell but it may have leaked at one point me someone repaired it but the repair now is not effective. Who knows. Starting to think the board is shot.

9646gt wrote on 2025-06-14, 00:44:

The Soyo keeps giving me memory errors (long beep) now. I finally had it working minus the IO card not doing as it should which I guess was leading to the black screen after initial post. I figured out that one of the 72pin slots was causing errors because it stopped freezing with just one slot used. I notice the slot seemed just a tad loose so I tried to reflow the solder connection on the bottom and added some fresh solder but didn’t help and after booting a few times I’m now just getting a memory errors al together.

I found some corrosion on the cmos clear jumpers and cleaned the area with vinegar. It’s odd since it uses a coin cell but it may have leaked at one point me someone repaired it but the repair now is not effective. Who knows. Starting to think the board is shot.

I have an 025N2 that used to have a varta battery in that spot. It leaked and got into that clear CMOS jumper area among other nearby areas. Have you checked under the keyboard controller IC for more corrosion? How are your voltages looking? Even if the board never had a varta, perhaps another board that had a leaky one was stacked on top of it at some point.

Have you used the clear CMOS jumper on this board? I've seen an Award BIOS with BIOS defaults loaded + general tweaking seem to work OK most of the time after a battery replacement but still exhibit odd behavior on occasion until the CMOS jumper was used to truly clear things out followed by loading BIOS defaults.

Any photos, btw?