A 553 KB PDF called simply 29040, indexed under schematics, which by its number most likely covers a 4 Mbit 29-series parallel flash memory datasheet; the manufacturer and package are not given in the name. Repair technicians consult it for the pinout, sector map, device ID codes and programming algorithm when working with a socketed or soldered BIOS chip. Since the file size equals that of 29040a, compare both. Read and back up the original chip with a programmer before any erase or write.
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 @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.