The smoke means something must have blown up. Boards don't produce smoke without a good reason.

Please post a quality picture of the board. The damage can be subtle. Next to ISA slots there are often tantalum capacitors on voltage lines.These could shorten to ground when old or knocked into.

Also since you mention the debug board. Could you accidentally put it the other way around?

I actually think I may have put the debug card on the wrong way. The smoke smell comes from the ISA slot I used to put the debug card.
I also noticed that the Intel cpu when the system is on gets hot, while the UMC cpu stays cold
Here a couple of pictures, the first is of the mb in general:
https://i.imgur.com/HMVUNAo.jpg

The second from where the smoke came out:
https://i.imgur.com/0JXZVJ3.jpg

Could have the umc cpu (bought as not tested) damage the mb? They are both 5v so I doubt it...

Edit: problem solved!
Nothing has blown up (maybe except the debug card at this point), simply the jumper setting I was counting from left to right, while they are from right to left, umc cpu works too!

Out of curiosity, is there a more updated bios version?
This is mine: https://imgur.com/a/Ix0WWOX
Biostar website is useless...

Thanks

Up, the card is (somewhat) working fine, the debug card works fine, but they are unable to work when put on the isa slots of such old motherboards.
I tested my 486 cpu collection (5v only): https://imgur.com/a/7PehlS1
Intel DX2 66: works
Intel DX2 50: works
Intel DX 50: doesn't work, even underclocking it to 33mhz
Intel SX 33: works
Amd DX 40: works even at 50mhz
Umc USX 40: the one on the right works fine, while the other on the left (NOS) doesn't work.

The non working cpus are confirmed working in another 486 mb. What I wonder is why one umc cpu works while the other doesn't? They are the same.
Why the DX50 doesn't work? While the amd dx 40 works even at 50 mhz?
I noticed that when a cpu doesn't work, it gets warm anyway.

Any suggestion please? Maybe a bios update could help, please?

So on my trials and tribulations with the vlb build, I found that probably the bios of this motherboard is corrupted.
When I try to enter the bios I get the waiting hourglass and nothing.
I tried to find a bios myself but without results.
That's the bios string:

Thanks

Bump, I tried to use bios of similar cards.
The one I got from phil's website is very old.
I tried the bios of the PCChips M912 v1.7 (486), but the system is unstable and the cache is not recognized.
I tried this bios: https://www.ultimateretro.net/en/motherboards/4230 and the system is apparently stable, but once again the cache is not recognized.

Any help please?

I have a similar board to yours, mine is a rev.7
I downloaded the bios just in case for my board off the vogons driver page here https://www.vogonsdrivers.com/getfile.php?fil … menustate=30,29
The bios dates match with my board but haven't compared them in the chip tester yet.
Are you sure your jumper settings are correct? I remember mine being unstable and later found out the cpu was set to 3.3 volts.

tacoman wrote on 2022-01-29, 11:28:

I have a similar board to yours, mine is a rev.7 I downloaded the bios just in case for my board off the vogons driver page here […]
Show full quote

I have a similar board to yours, mine is a rev.7
I downloaded the bios just in case for my board off the vogons driver page here https://www.vogonsdrivers.com/getfile.php?fil … menustate=30,29
The bios dates match with my board but haven't compared them in the chip tester yet.
Are you sure your jumper settings are correct? I remember mine being unstable and later found out the cpu was set to 3.3 volts.

Thank you very much for the bios, it works like a charme.
I think the motherboard has something wrong, sometimes it works fine and sometimes it doesn't. I'm sure about the jumper settings, I triple checked them.

Thank you again for the bios and sorry for the late answer.