I can't find any scans of the external modem PCBs, but the internal ISA ones have a 28f or 29f series EEPROM from what I've seen. Often there's a sticker on the

I can't find any scans of the external modem PCBs, but the internal ISA ones have a 28f or 29f series EEPROM from what I've seen. Often there's a sticker on them with firmware info, which suggests they're programmed before being soldered on the board (ie: no JTAG). The internal ones shouldn't be much different than externals, they just implement another serial interface. Would be a pain to desolder and resolder if it's a TSOP chip, but PLCC isn't too bad. You might have some better luck if you high-jack a compatible motherboard's floppy-disk BIOS update process to write a new binary. 56ks are not very expensive to buy off ebay.