Try a different memory module. Most importantly: Don't use EDO SIMMs, most 486 boards only accepts FPM SIMMs. Your symptoms look like the memory is "good enough" to be detected, but unable to run the system. This means that directly after detecting the memory (and then trying to use it), the system crashes.

Many thanks for reply.

I see, but unfortunately i don't have FPM memory right now.According to this auction link https://www.ebay.ca/itm/223554800087 it can boot with EDO i assume but i am not sure if this is EDO.Another thing i noticed BIOS sticker is different than mine.Is it possible to add EDO RAM support with BIOS update?(I don't know if this is possible.)

I have tried with Am486 DX4-100 SV8B same result.Also tried with 1 EDO SIMM installed and 2 EDO SIMM installed but no luck.Same D3 error.

Here is close shot of IC repair.(Sorry for flux residue.)

And here is backed up BIOS file for future reference or someone has same board:

Any comments are welcome.

whitepawn wrote on 2021-08-02, 16:50:

According to this auction link https://www.ebay.ca/itm/223554800087 it can boot with EDO

According to (the photo in) that auction link, the board uses the ALi 1429 chip (technically not a chipset, as it is a single chip). According to Wikipedia, that chipset, and even its successor chipset do not support EDO. That fits the timeline quite well, as typically only the latest 486 chipset of the big manufacturers supported EDO. EDO was not a common thing until 1994 or 1995.

whitepawn wrote on 2021-08-02, 16:50:

i assume but i am not sure if this is EDO.Another thing i noticed BIOS sticker is different than mine.Is it possible to add EDO RAM support with BIOS update?(I don't know if this is possible.)

EDO RAMs are incompatible with the way classic 486 chipsets use Fast Page Mode. The latest 486 chipsets support EDO RAMs by applying a workaround, which consists of a pulse on /WE after each read burst. For this to work, the chipset must be able to generate that pulse (sometimes only the latest revisions of a chipset support it. The UMC8881 northbridge is known to not support EDO RAM in all revisions for examplt), and the BIOS needs to detect the EDO RAMs and activate the extra pulse (which would just waste time with FPM RAM). So in theory, a BIOS update might make a board EDO compatible. In practice, chipset vendors provided EDO-capable BIOS code to the mainboard vendors a considerable time before they could deliver production hardware that supports EDO, so nearly all EDO-capable boards also come factory-equipped with an EDO-capable BIOS. The reverse it not true, though: Even non-EDO capable boards (e.g. old chipset revision) sometimes have a BIOS that would support EDO RAMs.

Because

1. EDO support was very uncommon at the time the M1429 was designed,
2. I couldn't find any reference claiming EDO support on the M1429 (not just Wikipedia says "no"),
3. Your symptoms are typical for EDO RAM in an FPM-only board,

I still expect that your problem is likely caused by using EDO RAM. If you don't know whether a specific memory module is EDO, try googling the part numbers on the memory chips on that module. EDO RAM datasheets contain either the phrase "EDO", "extended data out" or "hyper page mode", whereas FPM datasheets contain the phrase "FPM" or "fast page mode".

Many thanks for info.I have just bought FPM RAM and board booted fine so as you described EDO RAM was the problem.
Thanks again!