If #1 only boots with external cache disabled, perhaps it's due not to a bad mobo but some bad flash chips?

#3, M601, check the battery. I've seen a handful of cases where if the battery is completely shot the system wouldn't actually boot.

I would recommend to flash an bios update to these boards.. If the PCB circuitry look undamaged you could do that, maybe its just a corrupt bios.. I had one board here that doesnt work.. Flashed a new bios en board was running again.. Dont forget that these board are about 23 years old, then the quality of the bios part will go down after these times..

If the bios update also dont work, look for damaged capacitors or chips, broken capacitors and resistors can be replaced, and chips can be reflowed.

If the board have large broken traces i would desolder the usefull items from the board, like ram slot / cpu socket, cache chips, eprom.. ISA / VLB /PCI slots, keyboard en power connectors.
And dump the bare pcb.

I usually just throw them out. They have no value when they do not work. They have very little value as is unless they are sought after Asus MOBOs for example.

I used to throw away broken stuff, but I do not anymore. You can never tell what useless components might be needed in the future! A 72-pin slot to upgrade GUS or AWE32 with 72-pin SIMM, is a good example of how a something good can only be found in a pile of broken junk. So I keep them, I keep them all, put them in a large cardboard box in the garage and dig there once I need a victim for my soldering practice 😈

Btw, the last one looks like a fake Acer to me. I've got several Acer 486 parts, both OEM and retail, and they all have Acer serial number starting with a nine (probably the date code), for expample: 94136-1 48.43201.001 (A1GX motherboard) or 95328-1 48.56702.001 (8MB FPM SIMM). They also use a different font, something like default AutoCAD font and all my stuff has the words "Made in Taiwan R.O.C." printed in huge capital letters. And nothing on them says they belong to Acer.

IT seems the M601 needs a oscillator for the cpu to run, you need a twice the fsb speed osc.

If youre about to tossing them out, i would like to save them, can i buy them? especially the 8433
Every damage to the board, is repairable, except for broken Chipsets due to ESD, or you will have to source replacement ic's.
Please all be safe about ESD and protect your boards and components.

The ALI VLB board looks nice, probably the jumpers for FSB are between those ISA slots, can you make a clear macro picture that is also showing the top of those board print.
It is strange that there is a oscillator on there, probably you can switch between i fixed oscillator and a generated signal by the jumpers between the isa slot. Also take out the cache ram and see it it runs without looping/resetting also clean that sram pins with a screwdriver or such removing oxidation. there could be a bad contact.

What ram is installed on the 8433, what mem chip markings are on there?

Do you still have this motherboard or the bios ?

Half-Saint wrote on 2014-07-29, 09:51:

I have here three boards that are wonky or just not working: […]
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I have here three boards that are wonky or just not working:

1. MG 8001 Rev. 1.0 Acer 486 U.S. Technologies
- using nine UMC61256CK-20 cache chips
- boots with a DX2-50 CPU, don't know how to set it up for DX2-66
- only boots with external cache disabled in BIOS (endless reset loop if enabled)

Since 486 boards are quite rare, I would sell the to someone for the price of postage.

I have thrown away two PIII boards already that didn't work, one had no BIOS and some missing caps and another one was Intel 815 or something like that without AGP/ISA so completely useless. Some boards you get when you buy old computers are not worth saving.

moumiaq wrote on 2021-08-17, 18:32:

Do you still have this motherboard or the bios ?

No, sorry, I think I gave them away for the price of postage several years ago 😀