diff --git a/apps/zasm/io.asm b/apps/zasm/io.asm
index fb01c92..f620fc5 100644
--- a/apps/zasm/io.asm
+++ b/apps/zasm/io.asm
@@ -1,21 +1,25 @@
 ; *** Consts ***
 .equ	IO_MAX_LINELEN	0xff
 ; *** Variables ***
-ioGetCPtr:
-	.fill 2
-ioPutCPtr:
-	.fill 2
-ioLineBuf:
-	.fill IO_MAX_LINELEN+1
+.equ	IO_IN_GETC	IO_RAMSTART
+.equ	IO_IN_PUTC	IO_IN_GETC+2
+.equ	IO_IN_SEEK	IO_IN_PUTC+2
+.equ	IO_IN_TELL	IO_IN_SEEK+2
+.equ	IO_OUT_GETC	IO_IN_TELL+2
+.equ	IO_OUT_PUTC	IO_OUT_GETC+2
+.equ	IO_OUT_SEEK	IO_OUT_PUTC+2
+.equ	IO_OUT_TELL	IO_OUT_SEEK+2
+.equ	IO_LINEBUF	IO_OUT_TELL+2
+.equ	IO_RAMEND	IO_LINEBUF+IO_MAX_LINELEN+1
 
 ; *** Code ***
 
 ioGetC:
-	ld	ix, (ioGetCPtr)
+	ld	ix, (IO_IN_GETC)
 	jp	(ix)
 
 ioPutC:
-	ld	ix, (ioPutCPtr)
+	ld	ix, (IO_OUT_PUTC)
 	jp	(ix)
 
 ; Sets Z is A is CR, LF, or null.
@@ -27,9 +31,9 @@ isLineEnd:
 	cp	0x0a
 	ret
 
-; Read a single line from ioGetCPtr and place it in ioLineBuf.
+; Read a single line from ioGetCPtr and place it in IO_LINEBUF.
 ; Returns number of chars read in A. 0 means we're at the end of our input
-; stream, which happens when GetC unsets Z. Make HL point to ioLineBuf.
+; stream, which happens when GetC unsets Z. Make HL point to IO_LINEBUF.
 ; We ignore empty lines and pass through them like butter.
 ; A null char is written at the end of the line.
 ioReadLine:
@@ -43,8 +47,8 @@ ioReadLine:
 	jr	z, .loop1
 	; A contains the first char of our line.
 	ld	c, 1
-	ld	(ioLineBuf), a
-	ld	hl, ioLineBuf+1
+	ld	(IO_LINEBUF), a
+	ld	hl, IO_LINEBUF+1
 .loop2:
 	call	ioGetC
 	call	isLineEnd
@@ -59,7 +63,7 @@ ioReadLine:
 	xor	a
 	ld	(hl), a
 	ld	a, c
-	ld	hl, ioLineBuf
+	ld	hl, IO_LINEBUF
 	jr	.end
 .eof:
 	xor	a
diff --git a/apps/zasm/main.asm b/apps/zasm/main.asm
index 1eb2f3f..20c3a3e 100644
--- a/apps/zasm/main.asm
+++ b/apps/zasm/main.asm
@@ -7,14 +7,30 @@
 ; JUMP_UNSETZ
 ; JUMP_INTODE
 ; JUMP_FINDCHAR
+; JUMP_BLKSEL
 ; RAMSTART	(where we put our variables in RAM)
 
+jp	main
+#include "util.asm"
+.equ	IO_RAMSTART	RAMSTART
+#include "io.asm"
+#include "parse.asm"
+#include "literal.asm"
+#include "instr.asm"
+#include "directive.asm"
+.equ	SYM_RAMSTART	IO_RAMEND
+#include "symbol.asm"
+
 ; *** Code ***
-; Read file through GetC routine pointer at HL and outputs its upcodes through
-; the PutC routine pointer at DE.
+; Read file through blockdev ID in H and outputs its upcodes through blockdev
+; ID in L.
 main:
-	ld	(ioGetCPtr), hl
-	ld	(ioPutCPtr), de
+	ld	a, h
+	ld	de, IO_IN_GETC
+	call	JUMP_BLKSEL
+	ld	a, l
+	ld	de, IO_OUT_GETC
+	call	JUMP_BLKSEL
 	ld	hl, 0
 	ld	(curOutputOffset), hl
 .loop:
@@ -27,15 +43,6 @@ main:
 .stop:
 	ret
 
-#include "util.asm"
-#include "io.asm"
-#include "parse.asm"
-#include "literal.asm"
-#include "instr.asm"
-#include "directive.asm"
-.equ	SYM_RAMSTART	RAMSTART
-#include "symbol.asm"
-
 ; Increase (curOutputOffset) by A
 incOutputOffset:
 	push	de
diff --git a/parts/z80/blockdev.asm b/parts/z80/blockdev.asm
index 5ab541a..07ffa33 100644
--- a/parts/z80/blockdev.asm
+++ b/parts/z80/blockdev.asm
@@ -33,9 +33,11 @@ BLOCKDEV_TELL		.equ	BLOCKDEV_SEEK+2
 BLOCKDEV_RAMEND		.equ	BLOCKDEV_TELL+2
 
 ; *** CODE ***
-; Select block index specified in A
+; Select block index specified in A and place them in routine pointers at (DE).
+; For example, for a "regular" blkSel, you will want to set DE to BLOCKDEV_GETC.
 blkSel:
 	push	af
+	push	de
 	push	hl
 	ld	hl, blkDevTbl
 	cp	0
@@ -50,25 +52,32 @@ blkSel:
 .afterloop:
 	push	hl
 	call	intoHL
-	ld	(BLOCKDEV_GETC), hl
+	call	writeHLinDE
+	inc	de
+	inc	de
 	pop	hl
 	inc	hl
 	inc	hl
 	push	hl
 	call	intoHL
-	ld	(BLOCKDEV_PUTC), hl
+	call	writeHLinDE
+	inc	de
+	inc	de
 	pop	hl
 	inc	hl
 	inc	hl
 	push	hl
 	call	intoHL
-	ld	(BLOCKDEV_SEEK), hl
+	call	writeHLinDE
+	inc	de
+	inc	de
 	pop	hl
 	inc	hl
 	inc	hl
 	call	intoHL
-	ld	(BLOCKDEV_TELL), hl
+	call	writeHLinDE
 	pop	hl
+	pop	de
 	pop	af
 	ret
 
diff --git a/parts/z80/blockdev_cmds.asm b/parts/z80/blockdev_cmds.asm
index 7088417..4de0384 100644
--- a/parts/z80/blockdev_cmds.asm
+++ b/parts/z80/blockdev_cmds.asm
@@ -7,7 +7,10 @@ blkBselCmd:
 	ld	a, (hl)	; argument supplied
 	cp	BLOCKDEV_COUNT
 	jr	nc, .error	; if selection >= device count, error
+	push	de
+	ld	de, BLOCKDEV_GETC
 	call	blkSel
+	pop	de
 	xor	a
 	ret
 .error:
diff --git a/recipes/rc2014/sdcard/glue.asm b/recipes/rc2014/sdcard/glue.asm
index ef3f4c6..5844e65 100644
--- a/recipes/rc2014/sdcard/glue.asm
+++ b/recipes/rc2014/sdcard/glue.asm
@@ -5,10 +5,10 @@ RAMEND		.equ	0xffff
 ACIA_CTL	.equ	0x80	; Control and status. RS off.
 ACIA_IO		.equ	0x81	; Transmit. RS on.
 
-jr	init
+jp	init
 
 ; *** JUMP TABLE ***
-; Why not use this unused space between 0x02 and 0x28 for a jump table?
+; Why not use this unused space between 0x03 and 0x38 for a jump table?
 	jp	printstr
 	jp	printHex
 	jp	sdcInitialize
@@ -24,20 +24,6 @@ jr	init
 .fill	0x38-$
 jp	aciaInt
 
-init:
-	di
-	; setup stack
-	ld	hl, RAMEND
-	ld	sp, hl
-	im 1
-	call	aciaInit
-	xor	a
-	call	blkSel
-	call	shellInit
-
-	ei
-	jp	shellLoop
-
 #include "core.asm"
 ACIA_RAMSTART	.equ	RAMSTART
 #include "acia.asm"
@@ -66,3 +52,19 @@ SHELL_EXTRA_CMD_COUNT .equ 3
 .equ SDC_PORT_CSLOW 5
 .equ SDC_PORT_SPI 4
 #include "sdc.asm"
+
+init:
+	di
+	; setup stack
+	ld	hl, RAMEND
+	ld	sp, hl
+	im 1
+	call	aciaInit
+	xor	a
+	ld	de, BLOCKDEV_GETC
+	call	blkSel
+	call	shellInit
+
+	ei
+	jp	shellLoop
+
diff --git a/recipes/rc2014/sdcard/jumptable.inc b/recipes/rc2014/sdcard/jumptable.inc
index b5b1ab5..36de374 100644
--- a/recipes/rc2014/sdcard/jumptable.inc
+++ b/recipes/rc2014/sdcard/jumptable.inc
@@ -1,11 +1,11 @@
-JUMP_PRINTSTR   .equ   0x02 
-JUMP_PRINTHEX   .equ   0x05 
-JUMP_SDCINITALIZE .equ   0x08 
-JUMP_SDCSENDRECV .equ  0x0b 
-JUMP_SDCWAITRESP .equ  0x0e 
-JUMP_SDCCMD     .equ   0x11 
-JUMP_SDCCMDR1   .equ   0x14 
-JUMP_SDCCMDR7   .equ   0x17 
-JUMP_SDCREAD    .equ   0x1a
-JUMP_SDCSETBLKSIZE .equ   0x1d
+JUMP_PRINTSTR   .equ   0x03
+JUMP_PRINTHEX   .equ   0x06 
+JUMP_SDCINITALIZE .equ 0x09 
+JUMP_SDCSENDRECV .equ  0x0c 
+JUMP_SDCWAITRESP .equ  0x0f 
+JUMP_SDCCMD     .equ   0x12 
+JUMP_SDCCMDR1   .equ   0x15 
+JUMP_SDCCMDR7   .equ   0x18 
+JUMP_SDCREAD    .equ   0x1b
+JUMP_SDCSETBLKSIZE .equ 0x1e
 
diff --git a/tools/emul/zasm.c b/tools/emul/zasm.c
index 3429a0d..b7772e2 100644
--- a/tools/emul/zasm.c
+++ b/tools/emul/zasm.c
@@ -11,7 +11,9 @@
  * Memory layout:
  *
  * 0x0000 - 0x3fff: ROM code from zasm_glue.asm
- * 0x4000 - 0xffff: Userspace
+ * 0x4000 - 0x47ff: RAM for kernel and stack
+ * 0x4800 - 0x57ff: Userspace code
+ * 0x5800 - 0xffff: Userspace RAM
  *
  * I/O Ports:
  *
@@ -19,7 +21,7 @@
  */
 
 // in sync with zasm_glue.asm
-#define USER_CODE 0x4000
+#define USER_CODE 0x4800
 #define STDIO_PORT 0x00
 
 static Z80Context cpu;
diff --git a/tools/emul/zasm_glue.asm b/tools/emul/zasm_glue.asm
index 0258d15..d8bbc64 100644
--- a/tools/emul/zasm_glue.asm
+++ b/tools/emul/zasm_glue.asm
@@ -1,6 +1,6 @@
 ; Glue code for the emulated environment
-.equ USER_CODE		0x4000
-.equ RAMEND		0xffff
+.equ RAMSTART		0x4000
+.equ USER_CODE		0x4800
 .equ STDIO_PORT		0x00
 
 jr	init	; 2 bytes
@@ -13,13 +13,15 @@ jp	unsetZ
 jp	intoDE
 jp	findchar
 jp	parseHexPair
+jp	blkSel
 
 init:
 	di
-	ld	hl, RAMEND
+	; We put the stack at the end of the kernel memory
+	ld	hl, USER_CODE-1
 	ld	sp, hl
-	ld	hl, emulGetC
-	ld	de, emulPutC
+	ld	h, 0	; input blkdev
+	ld	l, 1	; output blkdev
 	call	USER_CODE
 	; signal the emulator we're done
 	halt
@@ -39,3 +41,9 @@ emulPutC:
 	ret
 
 #include "core.asm"
+.equ	BLOCKDEV_RAMSTART	RAMSTART
+.equ	BLOCKDEV_COUNT		2
+#include "blockdev.asm"
+; List of devices
+.dw	emulGetC, 0, 0, 0
+.dw	0, emulPutC, 0, 0
diff --git a/tools/emul/zasm_user.asm b/tools/emul/zasm_user.asm
index 6913d4d..3224e16 100644
--- a/tools/emul/zasm_user.asm
+++ b/tools/emul/zasm_user.asm
@@ -7,8 +7,9 @@ JUMP_UNSETZ     .equ    0x0e
 JUMP_INTODE	.equ    0x11
 JUMP_FINDCHAR	.equ    0x14
 JUMP_PARSEHEXPAIR .equ    0x17
+JUMP_BLKSEL	.equ    0x1a
 
-.equ	USER_CODE	0x4000
-.equ	RAMSTART	0x6000
+.equ	USER_CODE	0x4800
+.equ	RAMSTART	0x5800
 .org	USER_CODE
 #include "main.asm"