[userbinator]

INT 21 is DOS, not BIOS.

You can still use INT 10 for BIOS video services.

Or just write into the text framebuffer directly; it's at B800:0000 in colour modes and B000:0000 in monochrome modes (it's surprising how much I still remember from when I exclusively did x86 PC Asm, ~3 decades ago.)

[fmakunbound]

Err I don't know... Didn't the bios set the video controller up for you? Not bare metal enough, I'm afraid. /s