...

/* draw_char: draws an ASCII char at x/y loc in framebuffer using 5x13 font:
 *
 *  params:
 * 	d0 - char value
 *	d1 - x value
 *	d2 - y value
 */

draw_char:
	movel	%d0, -(%sp)
	movel	%d7, -(%sp)
	movel	%d2, -(%sp)
	movel	%d1, -(%sp)
	movel	%a0, -(%sp)
	movel	%a1, -(%sp)
	movel	%d3, -(%sp)
	movel	%d4, -(%sp)
	movel	%d5, -(%sp)
	movel	%d6, -(%sp)

	movel	(ScrnBase), %a0
	mulsw	#(13 * 64), %d2

	movel	%d1, %d5
	mulsw	#5, %d5
	divuw	#8, %d5
	movew	%d5, %d6
	addal	%d6, %a0

	lsrl	#8, %d5
	lsrl	#8, %d5

	cmp	#0, %d5
	beq	even_stevens

even_stevens:
	addal	%d2, %a0

	sub	#32, %d0
	mulsw	#64, %d0

	/* Reset vars for image drawing: */
	lea	font_data(%pc), %a1 /* font data */
	addal	%d0, %a1 /* offset for font_data */

	movel	%d0, %d3

	movew	#13, %d1
fill_loop:

	movel	(%a1)+, %d0
	moveb	(%a0), %d7
	moveb	#0x80, %d2
	lsrb	%d5, %d0
	subb	#1, %d5
	asrb	%d5, %d2
	add	#1, %d5
	andb	%d2, %d7
	orb	%d7, %d0
	moveb	%d0, (%a0)+

	addal	#63, %a0	/* Move to next line */

check_dec:
	subi	#1, %d1
	bne	fill_loop

check_overflow:
	cmp	#3, %d5
	blt	draw_done
	movew	#8, %d4
	sub	%d5, %d4
	
	sub	#((13 * 64) - 1), %a0

	lea	font_data(%pc), %a1 /* font data */
	addal	%d3, %a1 /* offset for font_data */

	movew	#13, %d1
fill_loop2:

	movel	(%a1)+, %d0
	moveb	(%a0), %d7
	moveb	#1, %d2
	aslb	%d4, %d2
	lslb	%d4, %d0
	andb	%d2, %d7
	orb	%d7, %d0
	moveb	%d0, (%a0)+

	addal	#63, %a0	/* Move to next line */

check_dec2:
	subi	#1, %d1
	bne	fill_loop2

draw_done:

	movel	(%sp)+, %d6
	movel	(%sp)+, %d5
	movel	(%sp)+, %d4
	movel	(%sp)+, %d3
	movel	(%sp)+, %a1
	movel	(%sp)+, %a0
	movel	(%sp)+, %d1
	movel	(%sp)+, %d2
	movel	(%sp)+, %d7
	movel	(%sp)+, %d0

	rts

	...
.