Sony MBX-223 motherboard documentation for the M960/M970 project, L model, revision SA, packed in an 803 KB RAR. The smaller size versus the H model archive fits a lower-specification board with fewer circuits. It probably contains schematic pages for tracing power rails, checking signals and locating components and test points. The H model is a separate board, MBX-224, so make sure your PCB reads MBX-223 and matches the revision before relying on the drawings.
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 @generalschematics. 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)