Archive for Apple board 820-2273, labelled LIO, at 453 KB in RAR format. The tag suggests a left I/O daughterboard, which explains the small size compared with full logic board packages. No revision is given, so check the number printed on the PCB. Files like this let a technician follow USB, audio or power lines from the connector to the main board flex, test continuity and locate protection parts such as fuses, ferrites and ESD diodes when a port stops working or the board shorts.
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 @Mac_Shematic_Santale. 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.