Firmware archive for the Dell Inspiron 3521, with P28F001 in the name being Dell's regulatory model and type code for that notebook. The 3.07 MB RAR file contains the BIOS image for the system's SPI flash, no board number is stated, so identify the motherboard from the silkscreen before relying on it. Technicians use such dumps to revive a dead or bricked board via a hardware programmer. Read and save the existing chip first, and make sure the image size matches the flash part, otherwise it will not fit.
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 →