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

IBM PC Bios implementation: https://github.com/kaneton/appendix-bios/tree/master

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

Standard VGA Registers: https://corbatech.sourceforge.net/appleII/SecondSightVGARegisters.pdf

COMPAQ EGA Technical Reference Guide (1986): https://archive.org/details/trg-enhanced-color-graphics-board-1986-12/mode/1up

IBM VGA/XGA Technical Reference Manual (1992): https://archive.org/details/bitsavers_ibmpccardseferenceManualMay92_1756350/mode/1up

I/O ports

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

PIT8254

https://www.scs.stanford.edu/23wi-cs212/pintos/specs/8254.pdf

PIC8259

https://pdos.csail.mit.edu/6.828/2010/readings/hardware/8259A.pdf

Misc

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