BIOS firmware archive for the S451LN, with 305 in the name most likely being the BIOS version, though that is not certain. No brand or board revision is given. The 3.27 MB RAR should hold a full flash image, which can be written with a CH341A or similar programmer to restore a board with corrupt firmware. Check that the image size equals the SPI chip capacity and that the revision on your PCB matches. Always read and save the original chip contents before programming the new image.
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 →