my shortest asm program was 11 bytes + 2 bytes for the long jump, i exchanged the first 3 bytes that makes the long jump on boot sectors and the 8 characters on label (!) to make sure i erased by friends bios each time he booted
No int 21h, simple input values and no dos calls at all .. low level stuff
If you change a value in the cmos, each time you boot you get the famous Bios checksum error and you had to recheck every parameter
