Firmware dump for the Apple iMac 27-inch 5K Retina logic board 820-00609-A, packaged as a 4.29 MB RAR. Apple logic boards use the 820 prefix, with the letter suffix marking the revision. Technicians program such an image into the boot ROM with an SPI programmer when the machine fails to boot. A typical cause is a corrupted ROM after a failed update or a board swap. Read and save the original ROM first, because it contains serial and system-specific data that may need transferring. Check that the chip size 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 →