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Strange problem with 486 motherboard

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Reply 20 of 30, by evasive

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Let's see what the email gives us. As a result of this I saw some of the Soyo manuals were still missing so I uploaded those at elhvb.com. If the bios shows up it will go there as well

Reply 21 of 30, by Miphee

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evasive wrote on 2020-05-16, 20:29:

Let's see what the email gives us. As a result of this I saw some of the Soyo manuals were still missing so I uploaded those at elhvb.com. If the bios shows up it will go there as well

Thank you for the effort, appreciate it. I tried playing again with the 401-2 BIOS.
With it the computer only recognizes 1 video card and it's a flashing green artifacting mess. Beeps are completely normal, 1 beep indicating successful POST, 2 beeps indicating a CMOS mismatch, then I press F1 and the diagnostic card reports FF88, which means that it's in the BIOS setup.
So now I'm convinced that this is indeed a BIOS ROM issue and it won't work without the original software.

Reply 22 of 30, by evasive

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Tracked down 2 more possible owners one of which has an invalid email address. There's a working one on offer from slightly less than 100 euro, I asked that dealer for a bios backup. Fingers crossed we get something.

Reply 23 of 30, by Miphee

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evasive wrote on 2020-05-21, 09:11:

Tracked down 2 more possible owners one of which has an invalid email address. There's a working one on offer from slightly less than 100 euro, I asked that dealer for a bios backup. Fingers crossed we get something.

It would be awesome. I'm wondering why this board is so picky. I change my BIOS ROMs quite often and they almost always work in different boards.
I even tried a 386 AMI chip in a 486 VESA board and it worked... somewhat. AMI and AWARD versions are always interchangeable.
This board is a serious PITA.

Reply 24 of 30, by evasive

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I can only guess it was designed a bit more on the limits of the chipset so getting the timings wrong is causing havoc. As for the green artefacts usually this is because of oversignal so could be something is wrong with the board itself too, the power to the ISA slots having a bad capacitor or something.

Reply 25 of 30, by Miphee

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evasive wrote on 2020-05-21, 14:11:

I can only guess it was designed a bit more on the limits of the chipset so getting the timings wrong is causing havoc. As for the green artefacts usually this is because of oversignal so could be something is wrong with the board itself too, the power to the ISA slots having a bad capacitor or something.

I didn't actually check the tantalums or voltages yet so it's time to do that. I also downloaded every 486 BIOS files from 1992, maybe they are more compatible.
At this point I could just download every 486 related BIOS and test them one by one. 😁

Reply 26 of 30, by andunn

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Try the attached BIOS image, I dumped it from my non-working board. Looks exactly the same as your one, although mine is missing the correct KBC. Not sure if that is what prevents it from booting, might be something else broken as I got it in a non-tested state.

Reply 27 of 30, by computerguy08

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andunn wrote on 2021-09-08, 11:31:

Try the attached BIOS image, I dumped it from my non-working board. Looks exactly the same as your one, although mine is missing the correct KBC. Not sure if that is what prevents it from booting, might be something else broken as I got it in a non-tested state.

Could you take a photo of your board ?
There are multiple versions of the SY-020: http://www.win3x.org/uh19/motherboards/?showI … s=1&name=SY-020

Reply 28 of 30, by TheMobRules

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Miphee wrote on 2020-05-16, 06:22:

85C401 : 27 C°
85C402 : 65 - 75 C°
Nothing special here.

I don't know if the OP still has the board, but I just noticed this since the thread was resurrected and wanted to chime in. I have a board that uses the same SiS 85C401/2 chipset (ASUS ISA-486) and both of the ICs stay barely above room temperature, even when running at 50MHz FSB. So I'd say a temperature of 65-75C probably means there is a problem with that chip.

Reply 29 of 30, by andunn

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The board I have is either a SY-020M or SY-020P. Can't tell for sure as the model number sticker is missing. I've attached a hi-res photo of it.