Been working with my latest 486-machine a lot lately... PSU was broken, Dallas was broken, SCSI HDD was broken.

So, modded a flex-ATX PSU in old PSU casing, got new Dallas replacement and 4GB SD-card with SD-IDE converter (and ISA-IDE controller).
Then it refused to boot at all with over 500MB drives so got new BIOS from Fujitsu(!) and now it won't crash anymore and I can use the whole 4GB with EZ-drive.

Put some more memory 8MB to 20MB, swapped the old i486DX2/66 to Kingston Turbochip (Am5x86/133). Display controller is ATI Mach32 1MB VLB on motherboard and it is really fast. Chipset is Headland HTK340 (HTK320 is 386DX and HTK340 is for 486)
https://stason.org/TULARC/pc/motherboards/I/I … -DXG-D4-66.html

But now I want MR BIOS for this so I can tinker with BIOS settings, cache and memory timings and so. But I don't have a clue how to make a BIOS image which has extra modules: ICL BIOS will be MR BIOS and then ATI VBIOS and maybe SCSI BIOS (which this has also) on top of that.

Does anyone have any experience this kind of BIOS stuff?