23 Bytes for Munching Squares

gistfile1.txt

ORG 100h
SECTION .text

mov al, 13h        ; b0 13     ah == 0 taken from program start conditions
int 10h            ; cd 10     call the BIOS video interrupt

les bx, [bx]       ; c4 1d     program start conditions make this a short way to get es == 0a000
mov bx, 320        ; bb 40 01  == db 0bh 40h 01h

drawloop:
db 0f0h            ; 0f        add ax, si == db 01h 0f0h
stosb              ; aa        write data to screen, increment si/di

cwd                ; 99        dx = 0
mov ax, cx         ; 89 f8     load pixel address
div bx             ; f7 f3     ax = di / 320, dx = di % 320
xor ax, dx         ; 31 d0     munching square pattern
loop drawloop - 1  ; e2 f4

inc si             ; 46        next frame
jmp drawloop - 1   ; eb f1