Firmware archive for the Apple iMac 21.5 inch, model A1418, logic board 820-01061-A, packed as 4.27 MB RAR. Apple numbers its logic boards in the 820 series, with the suffix showing the revision. Such a dump is written to the board's SPI flash with an external programmer when an iMac will not boot or shows firmware corruption. Read and keep the original chip contents first, since serial and system data live there, and confirm the 820 number printed on the board.
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 →