yo ! for mainboards with soldered-on plcc32 flashroms it should be possible to use DIY secondary bioses.
ECS Elitegroup ship many of their boards with what they call "top hat flash". This is comprised of two adjacent plcc32 sockets with just a minor rewiring:
on the replacement socket, /OE (*out enable, active low*) is hardwired to /reset, thus activating the secondary chip.
on the pcb-side (the empty socket to flip over the pcb-soldered chip) /OE is wired to an upper NC pin 26 (not connected). *All other pins are wired 1:1* , both chips are in parallel. LPC is designed as a bus (mind the 3 ID pins). the top hat flash is populated with a W39V040AP FWH ( Winbond firmware hub).
I used to think that there might be some resistor or sth. to pull the pcb chip's */OE-/Init* high (= inactive) while the ECS mainboard would have like a voltage divider feeding */OE-/Init* to allow this. I do not quite get the idea why the pcb-bios does disable it outputs (if it does) when it is possible that both chips have /OE active (but the spare chip earlier in sync with /reset). any clue?
anyway, this type of circuit should work with most plcc32 FWH's . But use it at your own risk. --Quux