fsinan wrote on 2024-01-16, 21:38:

Found a new old stock 486 board printed 486UL-P101. It must be ECS or Chaintech. there are some variations out there with this b […]
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Found a new old stock 486 board printed 486UL-P101. It must be ECS or Chaintech. there are some variations out there with this board.

Mine has a bank of 30 pin rams and 2 banks of 72 pin slots. Exactly this 486ul-p101.jpg

Board boots with 4x256K 30 pin edos total of 1MB.

But I couldnt make it boot with 72 pin 4Mb and 8Mb modules of EDO. Only 72 pin or 72 pin and 30pin ram configs does not boot. Tried out both 72 pin banks together and single.

There seems to be there is no bios file out there for this board. It is listed using "EDO" but maybe I need FPM for 72 pins. Any ideas?

30 pin EDO RAM does not exist.

CoffeeOne wrote on 2024-01-16, 21:43:

30 pin EDO RAM does not exist.

OK, so what? Does it help me?

fsinan wrote on 2024-01-16, 21:38:

But I couldnt make it boot with 72 pin 4Mb and 8Mb modules of EDO. Only 72 pin or 72 pin and 30pin ram configs does not boot. Tried out both 72 pin banks together and single.

Try 72 pin FPM DRAM.

fsinan wrote on 2024-01-16, 21:56:

CoffeeOne wrote on 2024-01-16, 21:43:

30 pin EDO RAM does not exist.

OK, so what? Does it help me?

If you want us to help you, it helps if we know exactly what components your are trying to combine.

More specifically: very few 486 chipsets (and so motherboards) support EDO. So if you are trying to run 72p EDO SIMMs on them, that explains why they aren't working. We don't know what the 30p SIMMs are (probably FP - Fast Page - DRAM) but as we know they will not be EDO, so a 486 that doesn't support EDO would be - as you suspect- the prime cause of the behaviour you are observing. This board has an UM82C491F chipset. Its datasheet does not mention EDO, and as a rule that means it will not be supported.

If in doubt, post the chip codes from the largest chips on both modules. That should clear up what they are. If the 30p SIMMs are indeed FP and the 72p SIMMs are EDO, that's pretty conclusive. If the 72p SIMMs are also FP, something else is up.

Cleaned up the memory slots. Worked. In fact, it is working with every EDO chip memory I throw at it.

fsinan wrote on 2024-01-25, 22:21:

Cleaned up the memory slots. Worked. In fact, it is working with every EDO chip memory I throw at it.

Good, so the board takes EDO RAM in principle.
May I ask what EDO Simms did you throw at the board? What was the total RAM size?
Did you stability test the system with EDO Simms?