diff --git a/Makefile b/Makefile
index c1e27d9..a94de28 100644
--- a/Makefile
+++ b/Makefile
@@ -1,16 +1,34 @@
-BUILDDIR=.build
-_BIN= loader.bin
-BIN = $(patsubst %,$(BUILDDIR)/%,$(_BIN))
+AS = sdasz80
+LD = sdldz80
+OBJCOPY = sdobjcopy
+
+BUILD = .build
+
+TARGET = loader
+
+ASFLAGS = -plosff
+
+SRC = \
+src/loader.s \
+
+OBJ = $(addprefix $(BUILD)/, $(notdir $(SRC:.s=.rel)))
+vpath %.s $(sort $(dir $(SRC)))
 
 .PHONY: all clean
 
-all: $(BUILDDIR) $(BIN)
+all: $(BUILD) $(BUILD)/$(TARGET).bin
 
-$(BUILDDIR)/%.bin: src/%.z80 | $(BUILDDIR)
-	@zasm -w -i $< -o $@
+$(BUILD)/%.rel: %.s Makefile | $(BUILD)
+	$(AS) $(ASFLAGS) $@ $<
 
-$(BUILDDIR):
-	@mkdir $(BUILDDIR)
+$(BUILD)/$(TARGET).ihx: $(OBJ)
+	$(LD) -i $@ $(OBJ) -b MAIN=0x1100
+
+%.bin: %.ihx
+	$(OBJCOPY) -I ihex -O binary $< $@
+
+$(BUILD):
+	mkdir $@
 
 clean:
-	@rm -df $(BUILDDIR)/*.bin $(BUILDDIR)/*.lst .build
+	rm -fr $(BUILD)
diff --git a/src/loader.s b/src/loader.s
new file mode 100644
index 0000000..86e95b3
--- /dev/null
+++ b/src/loader.s
@@ -0,0 +1,29 @@
+;Retrieves CP/M from disk and loads it in memory starting at E400h
+;Uses calls to ROM subroutine for disk read.
+;Reads track 0, sectors 2 to 26, then track 1, sectors 1 to 25
+;This program is loaded into LBA sector 0 of disk, read to loc. 0800h by ROM disk_read subroutine, and executed.
+
+hstbuf    .equ (0x1200)      ; Will put 256-byte raw sector here
+disk_read .equ (0x029C)      ; Subroutine in 2K ROM
+cpm       .equ (0xFA00)      ; CP/M cold start entry in BIOS
+
+.area MAIN
+
+main:
+	ld c, #0x01              ; LBA bits 0 to 7
+	ld b, #0x00              ; LBA bits 8 to 15
+	ld e, #0x00              ; LBA bits 16 to 23
+	ld hl, (0xE400)          ; Memory address -- start of CCP
+
+loop:
+	call disk_read           ; Subroutine in ROM
+	ld a, c
+	cp #50
+	jp z,done
+	inc a
+	ld c, a
+	jp loop
+
+done:
+	out (0x01), a            ; Switch memory config to all-RAM
+	jp cpm                   ; lto BIOS cold start entry
diff --git a/src/loader.z80 b/src/loader.z80
deleted file mode 100644
index d1d3a2f..0000000
--- a/src/loader.z80
+++ /dev/null
@@ -1,30 +0,0 @@
-;Retrieves CP/M from disk and loads it in memory starting at E400h
-;Uses calls to ROM subroutine for disk read.
-;Reads track 0, sectors 2 to 26, then track 1, sectors 1 to 25
-;This program is loaded into LBA sector 0 of disk, read to loc. 0800h by ROM disk_read subroutine, and executed.
-
-#target bin
-#code _HOME, 0x1100
-
-hstbuf    equ 0x1200         ;will put 256-byte raw sector here
-disk_read equ 0x029C         ;subroutine in 2K ROM
-cpm       equ 0xFA00         ;CP/M cold start entry in BIOS
-
-main:
-	ld c,1                   ;LBA bits 0 to 7
-	ld b,0                   ;LBA bits 8 to 15
-	ld e,0                   ;LBA bits 16 to 23
-	ld hl,0xE400             ; Memory address -- start of CCP
-
-loop:
-	call disk_read           ;subroutine in ROM
-	ld a,c
-	cp 50
-	jp z,done
-	inc a
-	ld c,a
-	jp loop
-
-done:
-	out (1),a                ;switch memory config to all-RAM
-	jp cpm                   ;to BIOS cold start entry