I have encountered a few 486 boards that do that, never this model, but the ones I have seen had the same problem, the voltreg. Usually 5V chips bypassed it but sometimes not. Perhaps you should get a multimeter out and test that.

Otherwise it seems there are a few revisions out there, probably best double check the jumper settings are for the version you have. As a last thought, if you're using Write-Back processors, they might not work, because my SiS-based MSI doesn't post with them in, it only takes Write-thru.

HighTreason wrote:

I have encountered a few 486 boards that do that, never this model, but the ones I have seen had the same problem, the voltreg. Usually 5V chips bypassed it but sometimes not. Perhaps you should get a multimeter out and test that.

Otherwise it seems there are a few revisions out there, probably best double check the jumper settings are for the version you have. As a last thought, if you're using Write-Back processors, they might not work, because my SiS-based MSI doesn't post with them in, it only takes Write-thru.

Nothing wrong with WB, Sis 497/497 Acer AP43 works well with WB. Sis 471 might have problems being a VLB chip set, but that is not the case.

85C496 + 89C497. The only SiS I ever had aside from a DTK that was dead when I got it (barrel battery had already killed that one) and it never worked with them, I just assumed the chipset didn't support them... Though I did ditch that board in favor of a different one because it was particularly unreliable.

Battery is dead, replace it.
5v cpu should work when setting to 5v regulation it takes the psu 5v right?
It takes also some time to warm up.

No beeps doesn't mean all hope is lost.

Maybe there is something wrong with the EEPROM. Do you have a reader you can check it out with? I found on one of my boards that was not booting or beeping the pins on the BIOS were covered in some fine white corrosion. After I cleaned the legs, things worked again.

I got some progress with Rev C1 board. It does work with 5V CPU settings. It boots fine.

Rev C2 with the same settings doesn't work. On power up the lights blink on the keyboard and then nothing.

I could switch the BIOS chips as they are both socketed. It is interesting that C2 (I guess later revision) has older date on the BIOS chip (1995) as C1 has 1996. Maybe someone has already been playing with the BIOS chips.

My C1 has the same green sticker on the BIOS chip as C2 on the site mentioned in the 1st post. While my C2 pictured in the 1st post has the purple sticker.

Rev C2 on the Motherboards site:

Switched the BIOS chip and no improvement. I guess the Rev C2 is beyond my abilities 🙁

I'm using AMD 486DX2-80N with 5V setting, there are no markings on the chip what voltage does it require but the data-sheet I found says 3V. I guess I'm running it way over the limit - it does get really hot 🤣

Yes amd's are hot, they get me going.....

That is a 3.3v part so I wouldn't run it at 5v.