Firmware archive for a board identified only as NB8609 PCB MB V4, with no brand or model stated, which makes it hard to match with confidence. V4 likely marks the PCB version. The roughly 4 MB archive probably holds an SPI flash image to be written with a hardware programmer. Compare the NB8609 code and version printed on the board before using it, read and save the existing chip contents, and verify the image size matches the flash capacity.
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 →