I'm trying to fully revive one FIC 486-GVT-2 mobo. It just refuses to boot normally and the BIOS always hangs in the beginning of the POST process.

When the board is powered-on my POST analyzer always card shows the codes "0C, 03, 00, 04, 05" in this exact order and always hangs at code "05". The BIOS is Award core version 4.50G. I tried the original BIOS for this board ver. 3.03 and with some spare EEPROM the latest beta ver. 3.276GN1 (with removed half part for the onboard VGA option ROM) and there's absolutely no difference in the POST codes and the booting behavior regardless of which BIOS version I'm trying - the POST codes are always the same "0C, 03, 00, 04, 05" and the POST hangs at "05".

The motherboard is set with tested and working i486DX2-S 66 MHz. I tried different types of known-good 30-pin and 72-pin SIMM RAM modules in different combinations and there is no difference in POST codes.

I'm trying to understand what may be the problem according to these POST codes, but I don't know if descriptions for "Award PnP" or "Award Version 4.51PG" from https://blog.theretroweb.com/2024/01/20/award … post-codes-list are the right ones for the Award BIOS version 4.50G.

The board is not equipped with 3 V CMOS battery as the original one (BR1225) was soldered directly to the PCB and depleted, and I removed it, bit still I'm thinking how to add socket for CR2032. There are no broken traces, bulging or leaking electrolytic capacitors or any signs of physical damage on the board. I've triple checked all the jumper settings for the i486DX2-S 66 MHz CPU and measured all the 5, 12, -5. -12 V on the board and everything seems right.

I can't read anything from the PALCE16V8B-15 chip and I don't know it's purpose. My XGecu T48 shows only "zeroes" when read it using GAL16V8B settings. I don't know if this PAL chip is anti-read locked or if it's just scre*ed-up.

Any ideas what may preventing this motherboard from normal booting?