Hi All,
I’m looking for some technical advice on a mini ICL 386SX motherboard I’ve been trying to save from the scrap.
The board was originally missing many SMD components, but using detailed photos from CharlieGolf's same mobo (66MHz Brain on YouTube) I was able to identify the missing parts, successfully bringing it back to life. It was stable and running DOS games like Wolfenstein 3D without issue.

After expanding the memory with two new SIM module and power-cycling the system, it stopped POSTing. It is now stuck in an endless loop of 4 short beeps and 1 long beep, no display activity at all. Reversing the expansion (removing new RAM, clearing CMOS) does not help.
ISA Analyzer shows 00/--, LPT Analyzer shows 77/6F

I’ve spent a lot of time checking the memory subsystem (CAS, RAS, WE, Parity, and Data lines) with an oscilloscope. Interestingly, I was trying in the wrong direction, the board will succesfully POST and enter BIOS if I replace the original BIOS with a "MrBIOS" universal image for the same Tact83000 chipset, and with and ISA VGA card. (with original BIOS the ISA VGA doesn't change anything)
(it was also not simple, because the bigger 27c512 eprom requirements - but I solved it with disconnect VCC from EPROM leg one, and connect the A15 to Address 15 on ISA bus)
However, this is only a partial fix because the MrBIOS image fails to initialize the onboard ATi VGA and I/O chips, rendering the board's unique integrated features useless.
So I need to get it working with an original BIOS.

The BIOS was dumped from the original 27C256(32KB) EPROM using a T48 programmer. Gemini AI tells me this is a good BIOS, because the checksum is valid. But the data looks unusual, only about 8KB contains data, different from other 386SX BIOS files.
I am confused, the size and content are concerning, its very small for such an integrated board.

Can anyone with greater knowledge verify if the BIOS dump is corrupted?
Does anyone have a working original BIOS file for this motherboard?
Any idea how this motherboard could be made to function fully again?

Motherboard Specs: ICL CL386S
https://theretroweb.com/motherboards/s/icl-cl … 386s,-cs386s-25
The (potentially corrupt) original BIOS dump is attached.

Thank you very much,
vrob98