BIOS image for a Sony VAIO motherboard MBX-195, also marked M791, revision 1.0, compressed into an 835 KB RAR. MBX numbers are Sony's own board identifiers, used on VAIO notebooks such as the VGN-NS series. The small size suggests a 1 MB class flash chip, but check the extracted file. It is written to the SPI flash with a programmer to recover from a corrupt update or a password lock. Back up the original chip and make sure the image size matches the chip before writing.
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 →