An archive of repair files. Shared as “A840-mb-d.rar” — a .rar file, 142 KB.
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 @schematics_bios. 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.
7-ZipWinRARThe Unarchiver (macOS)