See http://plus.google.com/+ChrisMcClelland/posts/Zf4wswFodTv

HOWTO

$ # Fetch the ACME source code...
$ wget -qO- http://www.esw-heim.tu-clausthal.de/~marco/smorbrod/acme/current/acme093testing.tar.bz2 | bunzip2 -c | tar xf -
$
$ # Build it...
$ cd acme093testing/src/
$ sed -i 's/$(CC) $(LIBS)\(.*\)/$(CC)\1 $(LIBS)/g' Makefile
$ make -s 2>/dev/null
$
$ # Fetch the DOS 3.1 binary disk image...
$ wget -q -O dos3.1.d13 'http://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Software/Operating%20Systems/Apple%20DOS/Disk%20Images/Apple%20DOS%203.1%20Master.d13'
$
$ # Fetch & view the DCBSUP subroutine, tweaked to assemble with ACME...
$ cp ../../dcbsup.s .
$ cat dcbsup.s
	!to "dos3.1.bin", plain
	* = $8000
	FCBDCB = $3505
	DCBLEN = $2D
	CCBVOL = $34F3
	DCBVOL = $352D
	CCBDRV = $34F4
	DCBDRV = $352C
	CCBSLT = $34F5
	DCBSLT = $352B
	DCBVTN = $352E
DCBSUP
	LDA	#0
	TAX
F01	STA	FCBDCB, X	;CLEAR DCB
	INX
	CPX	#DCBLEN
	BNE	F01
	;;
	LDA	CCBVOL		;MOVE VOL
	EOR	#$FF		;INVERT VOL BITS
	STA	DCBVOL
	LDA	CCBDRV		;MOVE DRIVE
	STA	DCBDRV
	LDA	CCBSLT		;GET USER SPEC SLOT
	ASL			;SLOT*16
	ASL
	ASL
	ASL
	TAX
F01A
	STX	DCBSLT
	LDA	#17
	STA	DCBVTN
	RTS
$
$ # Assemble the code, producing "dos3.1.bin"...
$ ./acme dcbsup.s
$ od -A n -w1024 -tx1 dos3.1.bin
 a9 00 aa 9d 05 35 e8 e0 2d d0 f8 ad f3 34 49 ff 8d 2d 35 ad f4 34 8d 2c 35 ad f5 34 0a 0a 0a 0a aa 8e 2b 35 a9 11 8d 2e 35 60
$
$ # Finally, search for this machine code in the disk image...
$ od -w1024 -tx1 dos3.1.d13 | grep -oba "$(od -A n -w1024 -tx1 dos3.1.bin)"
20002: a9 00 aa 9d 05 35 e8 e0 2d d0 f8 ad f3 34 49 ff 8d 2d 35 ad f4 34 8d 2c 35 ad f5 34 0a 0a 0a 0a aa 8e 2b 35 a9 11 8d 2e 35 60