Firmware pair for the Sony M850 mainboard MBX-205, a 923 KB ZIP; the name lists U12 and U46, which likely are the reference designators of two chips that each receive their own image. Locate those positions on the board before programming, as writing the wrong file to a chip will leave the laptop dead. Use an external programmer and save each original chip first. Confirm the MBX-205 marking on the PCB and check every file size matches the capacity of its target 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 .zip file
Compressed archive that every operating system opens without extra software.
Back up your own chip before writing any dump, and match the full board number and revision. Flashing guide →