BIOS firmware archive for the Apple A1312 iMac logic board 820-2828, revision A, packed as a RAR of about 6.66 MB. It is meant for restoring the boot ROM when the machine shows no chime, a black screen or a corrupted firmware after a failed update. Extract the image and write it to the SPI flash with a programmer such as a CH341A or RT809H. Before writing, read and save the original chip contents, confirm the 820-2828 number silkscreened on the board, and check that the image size equals the chip capacity.
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 →