A company I occasionally do support for has a profitable legacy system that runs on 486 or lower PCs. Supplier of product out of busiess. One PC died and they c

A company I occasionally do support for has a profitable legacy system that runs on 486 or lower PCs. Supplier of product out of busiess. One PC died and they couldn't get any more. I found a manufacturer of current PC104 boards with a 486 CPU. moved the software across to those. It nearly worked but would occasionally crash. I asked a genius friend to have a look at it. He got out his trusty DOS debug floppy disks, footled around for a few days working out what was wrong (slightly incompatible implementation of serial port in the SoC on the PC104 boards, plus crap code in the original system), hand-assembled a workaround and wrote it in to blank space on the original executable, and presto! the system has been running reliably on the new hardware for a couple of years now.