Documentation references for old PCs

Some resources to understand how the hardware / software worked on those machines

Dos and BIOS interrupts

http://www.techhelpmanual.com/95-interrupts_and_bios_services.html

https://helppc.netcore2k.net/topics

https://www.ctyme.com/intr/int.htm

CPU

Instructions reference: https://www.felixcloutier.com/x86/

Instructions parsing: http://www.c-jump.com/CIS77/CPU/x86/index.html

VGA

Bochs VGA Bios source code: https://github.com/miurahr/vgabios/tree/master

I/O ports

XT, AT and PS/2 I/O port addresses: https://bochs.sourceforge.io/techspec/PORTS.LST

Misc

Hardware Check program: https://winworldpc.com/product/checkit/1x