i have 1920x1200 lcd monitor (multiple inputs, DSUB +DVI +DP), which is not always select properly aspect, and also not always allow manual selection for this.
also i use now integrated video in i7 3770 cpu, what for me enough.

for sample, it often select properly aspect on DSUB input, except standard vga mode 720x400, which really 16:10, but i want see it as 4:3 🤣
on DVI input my monitor mostly newer show 4:3 aspect, except one old windows game...
on DP i now cant check, as have not cable.

but when i connect this monitor to DVI on other comp for testing, i see 4:3 more then often...
so i now think, that problem is just wrong programmed (by UEFI on POST procedure) CRT registers (which 3xxh).
and i want try change this registers, may be this help switch monitor to 4:3 aspect? 😎
i can do it via assembler IN/OUT instructions, but me more want do it interactively... 🤣

may be there already exist that program? for DOS sure...