Schematic for the IBM ROME project, revision 3.5 according to the file name, supplied as a 1.62 MB PDF. The code name does not by itself identify the retail ThinkPad model, so verify the board markings before using it for measurements. A later revision 4.0 of the same design is also catalogued, and the two may differ in component values or circuitry. Technicians use such sheets to follow supply rails, find test points and identify what loads a shorted line. Any standard PDF viewer opens it.
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 @schematicslaptop. 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.