Minor update - Just as I was posting this I reassembled the system on my desk. Started it, No crackle, no smell.

The CPU fan is working again and the S3 trio is getting warm...but nothing on the display.

My display works no issue when I attach my Pentium 150, 166MMX or 486 systems to it using the same display cable.

I do have a multimeter and one of those Zoyi ZT-MD2 Capacitor testers after watching philscomoputer lab review one. I am wondering if I can poke around with these to try to figure out what went bad or where to start with repairing

Are you sure it wasn't the PSU that caused the pop/smell? I've had NOS PSUs fail so I wouldn't immediately rule that out. It might be worth testing the S3 trio on a different board to make sure that isn't the component that died as well.

None of the above.
I'll put it up on ebay making it very clear the item is broken, In the title, in the description and listing type.
And will list in the description as clear as possible what I know is wrong with it.

Starting price of just $1, as you say it's more about saving it from landfill then making profit.
However sometimes you actually do make a nice little sum of money from the sale.

TheMLGladiator wrote on 2025-11-25, 04:51:

Are you sure it wasn't the PSU that caused the pop/smell? I've had NOS PSUs fail so I wouldn't immediately rule that out. It might be worth testing the S3 trio on a different board to make sure that isn't the component that died as well.

This. If there is a sound and a smell, there are usually visible signs. Burn holes on tantalums can be relly small, though.

I’d check all the voltage rails to rule PSU out.

This evenings update.

I have now tried 3 different AT PSUs. Note that only one of my PSUs (the new old stock Antec) was connected using the original IBM PC PSU connectors. These are the ones that if you did not put the black connectors next to each other you blew the board to kingdom come.

My other 2 PSus are Enlight 300W and using the more modern 20 pin ATX main power connectors. You will also see a PC Power Supply Tester in the latest photo.

I tried various PCI graphics cards including a trident, S3 trio and Diamond Stealth. All no picture on the monitor. Then I moved to the onboard video chip, note the cable in the photo, and changed the jumper so it would be active. Still no picture.

I changed monitors and VGA cables. Still no joy.

I changed RAM chips many many times...and am wondering if this may be the issue.

The crackling sound never repeated, and the smell has disappeared. As mentioned no sign of any burns.

Please note there IS power running on the board. At the bottom of the board next to the yellow chipset you can see a on off switch cable. It works and turns the board on. The CPU fan connected to the board, comes on. There is no beep sound from the speaker but thats ok as i think it is faulty and have 2 on order so i hope to at least hear a beep or many beeps if there is an error. We will see.

Side note: in case you are wondering the oversized CPU fan is NOT socket 7. I think from a 775 cooler. The Pentium 100 CPU has a passive heat sink almost "glued" on and was like this in my IBM Aptiva. There is a chassis fan in the Aptiva a breeze over it.

chinny22 wrote on 2025-11-25, 04:54:

None of the above. I'll put it up on ebay making it very clear the item is broken, In the title, in the description and listing […]
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None of the above.
I'll put it up on ebay making it very clear the item is broken, In the title, in the description and listing type.
And will list in the description as clear as possible what I know is wrong with it.

Starting price of just $1, as you say it's more about saving it from landfill then making profit.
However sometimes you actually do make a nice little sum of money from the sale.

I live in Malaysia (I am a Kiwi btw) so shipping from here will likely freak most people out - amusingly when I buy stuff off ebay from the UK, Germany or the USA all the time and as I expect a heft shipping price i don't even think of it anymore.

But yes this is a good idea if I really can't fix it.

Dont ever use old computers if you dont have the will to troubleshoot. Learn the basics and get a base with proper tools (the basics are cheap)

I have a baby AT Tekram MVP3 board and a Soyo ATX board both waiting repair on some far distant day.

Some good but confusing developments. Thinking outside the box i was wondering if the issue might be the CPU. I had a Pentium 100 in it for testing and it had booted that one time with it.

So i put in a AMD K6-2 450, changed the jumpers to get as close to the multiplier and voltage as i could and hey presto!! It booted!!! I suspect this CPU came a fair bit later after the MB as the MB does not have a 100Mhz FSB or a voltage that matches exactly

Next i swapped the AMD out and put a 166MMX into it, changed the jumpers for this CPU and ...fail!?!

Tried the 100Mhz Pentium, changed jumpers for multiplier, voltage and CPU type (P54C) and again fail.

Put the AMD back in and successful boot.

The reason has me stymied, as after making PCs for 40 years, and being well aware of what jumpers need to be configured, I have never seen this peculiar "feature" before.

I will try to find the latest BIOS, flash it, and hopefully whatever bug is causing this issue will be squashed. Including photos to show that yes it alive! Hopefully this concludes this escapade.

I will give what will likely be the final summary of this posting.

Firstly thank you for everyone who did assist in the troubleshooting. Meant a lot to me.

This evening I updated the BIOS to the last one that was released, then had a friend assist as we went over all of the settings and jumpers on the board to ensure I hadn't made any mistakes. They were all correct.

Despite the BIOS update, and the extra pair of eyes, I can say that this particular m571 board does not like or see either my 100MHZ Pentium, nor my 166MMX CPU. Both are working on my other Socket 7 boards. First time I have ever encountered this issue and searching online showed up nothing useful.

Thanks to the resources at http://m571.com/m571/index.htm I was able to set the board to use my AMD K6-2 450Mhz at its full 450Mhz speed.

So mission accomplished as far as it can be. Cheers!

KiasuKing wrote on 2025-11-27, 15:18:

Despite the BIOS update, and the extra pair of eyes, I can say that this particular m571 board does not like or see either my 100MHZ Pentium, nor my 166MMX CPU. Both are working on my other Socket 7 boards. First time I have ever encountered this issue and searching online showed up nothing useful.

It is unusual when a board will accept one type of processor, but not others, despite being purportedly supported.

For diagnosing this, I would look which jumpers are different for the K6-2 settings versus the Pentium or Pentium MMX. It's possible there is a bad contact or broken trace that could be impacting the settings for the Pentium processors.

Another thing to check is the CPU voltage with the different jumper settings for different voltages.

If I’m attached to it or it’s an uncommon component I try to convince myself that someday I’ll have the skill level to tackle it. And sometimes, as above, things just need a little time and effort chipping away at the troubleshooting.

Shponglefan wrote on 2025-11-27, 15:30:

KiasuKing wrote on 2025-11-27, 15:18:

Despite the BIOS update, and the extra pair of eyes, I can say that this particular m571 board does not like or see either my 100MHZ Pentium, nor my 166MMX CPU. Both are working on my other Socket 7 boards. First time I have ever encountered this issue and searching online showed up nothing useful.

It's possible there is a bad contact or broken trace that could be impacting the settings for the Pentium processors.

Yes indeed! Troubleshooting that is beyond my knowledge, and eyesight. I mentioned a small "crackle" sound when I first got the board and this would tend to support that. I have been very careful double checking the voltage (JP6 on this board) and CPU type ( JP8 ). I have never dabbled with overclocking so am a little wary of cooking my Intel CPUs by putting too many volts into them.

I even checked each pin on the Intel CPUs to see if there was something wrong with them

I fully concur with the oddness. Never in my many years of experience have I ever seen such a situation and is why I had a friend assist me last night to ensure I wasn't missing something.