EFI firmware for the Apple A1286 MacBook Pro logic board 820-2850-A, the A suffix being the revision, intended for a 4MB flash chip and stored as a 4.63 MB RAR. Apple uses 820-numbered logic board designations. The dump is written to the SPI ROM with a programmer to fix boards without chime or with a firmware lock. Save the original contents first, since they hold the serial and network data, and confirm that the board number on the PCB and the ROM size agree.
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 →