RAR package for the FIC PCA50 board at revision 1.0, about 1.57 MB, from First International Computer, a Taiwanese ODM whose designs were sold under many brands. A 1.0 revision usually indicates a later or production-level drawing set compared with earlier 0.x releases. The archive likely holds schematics; extract with WinRAR or 7-Zip. Use them to follow power circuits and signal paths, and verify that the PCB carries PCA50 without a suffix and Rev 1.0 before relying on them.
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 @IT_SERVICE_WORLD. 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.