Firmware dump for an Apple MacBook A1181 built on logic board 820-1889-A, which the name tags as M42c and MBP, delivered as an 815 KB RAR archive. Apple calls this the EFI or boot ROM rather than a BIOS, and it lives on an SPI flash chip on the logic board. Technicians rewrite such an image with a programmer when a machine powers on but will not chime or boot. Read and save the original chip contents first, check the capacity of the fitted flash part, and confirm the 820 number on the board matches.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @biosarchive. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.
Back up your own chip before writing any dump, and match the full board number and revision. Flashing guide →