ychh0 wrote on 2023-05-10, 05:05:
I wonder if there is MR BIOS for OPTi 82C802/82C601 486 mainboard.
Well you seem to have a very tricky case.
First, I don't think I ever saw any mentions of OPTi 82C802 in MR BIOS docs. In fact, it seems to be a pretty rare chipset — on TRW there is only one board with it. We do have images for 82C802G, which should be just 82C802 with added power management features. See the image V085B4C1 on the OPTi sheet in this spreadsheet. There's a high chance 802 should work with a BIOS made for 802G. Another candidate would be 895 image (seems to be 802G with a different memory configuration), we have one as well. Not sure about 801. The download images are on the first page.
Second, looking at your board it seems like the BIOS sticker is on a DIP-40 chip, so they've likely labelled the keyboard controller chip as the BIOS, and the actual BIOS is on the right from it. It's a DIP32 chip, so I suspect it's 128KB while the system BIOS is probably 64KB. If that's the case, it's probably a combined BIOS that includes both the system BIOS and the videocard BIOS for the Cirrus Logic chip. None of the MR BIOS images except for some very late Socket 7 ones include the video BIOS and I haven't ever heard about anyone successfully merging MR BIOS with a video BIOS. Haven't tried personally, maybe someone else can chime in on this — I know people have done this with NCR SCSI stuff.
So in short, we have the images that are very likely to work with your chipset, but the video BIOS part is probably a challenge here. And I definitely wouldn't attempt this without a chip programmer.