diff --git a/src/Makefile b/src/Makefile
index 8b71d37..32759fa 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -1,7 +1,7 @@
 CLI=rk65c02cli
 CLI_OBJS=rk65c02cli.o
 
-LIB_OBJS=rk65c02.o bus.o instruction.o emulation.o debug.o
+LIB_OBJS=rk65c02.o bus.o instruction.o emulation.o debug.o device_ram.o
 LIB_SO=librk65c02.so
 LIB_STATIC=librk65c02.a
 
diff --git a/src/bus.c b/src/bus.c
index d7c8960..39c47f1 100644
--- a/src/bus.c
+++ b/src/bus.c
@@ -9,24 +9,69 @@
 
 #include <sys/types.h>
 
+#include <utlist.h>
+
 #include "bus.h"
 
+#include "device_ram.h"
+
 #define RK65C02_BUS_SIZE	64*1024
 
+void
+bus_device_add(bus_t *b, device_t *d, uint16_t addr)
+{
+	device_mapping_t *dm;
+
+	dm = (device_mapping_t *) malloc(sizeof(device_mapping_t));
+
+	dm->dev = d;
+	dm->addr = addr;
+
+	LL_APPEND((b->dm_head), dm);
+}
+
 uint8_t
 bus_read_1(bus_t *t, uint16_t addr)
 {
 	uint8_t val;
-//	val = t->space[addr];
-/*	printf("bus READ @ %x value %x\n", addr, val); */
+	device_mapping_t *dm;
+	device_t *d;
+
+	LL_FOREACH(t->dm_head, dm) {
+		d = dm->dev;
+
+		if (dm->addr == 0)
+			val = d->read_1(d, addr);
+		/* 
+		 * else
+		 * Check if address is inside of given device range, calculate
+		 * offset.
+		 */	
+
+	}
+	printf("bus READ @ %x value %x\n", addr, val); 
 	return val;
 }
 
 void
 bus_write_1(bus_t *t, uint16_t addr, uint8_t val)
 {
-/*	printf("bus WRITE @ %x value %x\n", addr, val); */
-//	t->space[addr] = val;
+	device_mapping_t *dm;
+	device_t *d;
+
+	LL_FOREACH(t->dm_head, dm) {
+		d = dm->dev;
+
+		if (dm->addr == 0)
+			d->write_1(d, addr, val);
+		/* 
+		 * else
+		 * Check if address is inside of given device range, calculate
+		 * offset.
+		 */	
+
+	}
+	printf("bus WRITE @ %x value %x\n", addr, val); 
 }
 
 bus_t
@@ -34,15 +79,23 @@ bus_init()
 {
 	bus_t t;
 
-//	t.space = (uint8_t *) malloc(RK65C02_BUS_SIZE);
-
-//	assert(t.space != NULL);
-
-//	memset(t.space, 0, RK65C02_BUS_SIZE);
+	t.dm_head = NULL;
 
 	return t;	
 }
-/*
+
+bus_t
+bus_init_with_default_devs()
+{
+	bus_t t;
+
+	t = bus_init();
+
+	bus_device_add(&t, device_ram_init(), 0x0);
+
+	return t;
+}
+
 bool
 bus_load_buf(bus_t *t, uint16_t addr, uint8_t *buf, uint16_t bufsize)
 {
@@ -53,13 +106,13 @@ bus_load_buf(bus_t *t, uint16_t addr, uint8_t *buf, uint16_t bufsize)
 	// XXX: add sanity checks 
 
 	while (i < bufsize) {
-		t->space[addr+i] = buf[i]; // XXX: overflow addr
+		bus_write_1(t, i, buf[i]); // XXX: overflow addr
 		i++;
 	}
 
 	return true;
 }
-
+/*
 bool
 bus_load_file(bus_t *t, uint16_t addr, const char *filename)
 {
diff --git a/src/bus.h b/src/bus.h
index 605cec9..76ac8b8 100644
--- a/src/bus.h
+++ b/src/bus.h
@@ -9,7 +9,7 @@
 #define RK65C02_BUS_SIZE	64*1024
 
 struct bus_tag {
-	device_t *device_head;
+	device_mapping_t *dm_head;
 };
 
 typedef struct bus_tag bus_t;
@@ -18,7 +18,7 @@ uint8_t bus_read_1(bus_t *, uint16_t);
 void bus_write_1(bus_t *, uint16_t, uint8_t);
 bus_t bus_init();
 void bus_finish(bus_t *);
-bool bus_load_file(bus_t *, uint16_t, const char *);
+//bool bus_load_file(bus_t *, uint16_t, const char *);
 bool bus_load_buf(bus_t *, uint16_t, uint8_t *, uint16_t);
 
 #endif /* _BUS_H_ */
diff --git a/src/device.h b/src/device.h
index aa224f6..c7fcb71 100644
--- a/src/device.h
+++ b/src/device.h
@@ -1,27 +1,24 @@
 #ifndef _DEVICE_H_
 #define _DEVICE_H_
 
-//#include "bus.h"
-
-typedef struct device_space_t {
-	//uint8_t id;
-	uint16_t address;
-	uint16_t size;
-
-	uint8_t (*read_1)(uint16_t addr);
-	void (*write_1)(uint16_t addr, uint8_t val);
-
-	void *aux;	/* any additional space-specific data */
-
-	struct device_space_t *next;
-} device_space_t;
-
 typedef struct device_t {
 	const char *name;
-	device_space_t *space_head;
 
-	struct device_t *next;
+	uint16_t size;
+
+	uint8_t (*read_1)(void *, uint16_t doff);
+	void (*write_1)(void *, uint16_t, uint8_t val);
+
+	void *config;
+	void *aux;	/* any dev space-specific data */
 } device_t;
 
+typedef struct device_mapping_t {
+	device_t *dev;
+	uint16_t addr;
+
+	struct device_mapping_t *next;
+} device_mapping_t;
+
 #endif /* _DEVICE_H_ */
 
diff --git a/src/device_ram.c b/src/device_ram.c
index a7757b7..1a15338 100644
--- a/src/device_ram.c
+++ b/src/device_ram.c
@@ -1,8 +1,57 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <string.h>
+
 #include "bus.h"
 #include "device.h"
 
-bool
-device_ram_add(bus_t *t)
+#define RAM_SIZE 0xDFFF /* should be configurable */
+
+uint8_t
+device_ram_read_1(void *vd, uint16_t offset)
 {
-	
+	device_t *d;
+	uint8_t *ram;
+
+	d = (device_t *) vd;
+	ram = d->aux;
+
+	return ram[offset];
 }
+
+void
+device_ram_write_1(void *vd, uint16_t offset, uint8_t val)
+{
+	device_t *d;
+	uint8_t *ram;
+
+	d = (device_t *) vd;
+	ram = d->aux;
+
+	ram[offset] = val;
+}
+
+device_t *
+device_ram_init()
+{
+	device_t *d;
+
+	d = (device_t *) malloc(sizeof(device_t));
+
+	assert(d != NULL);
+
+	d->name = "RAM";
+	d->size = RAM_SIZE;
+
+	d->read_1 = device_ram_read_1;
+	d->write_1 = device_ram_write_1;
+
+	d->aux = malloc(RAM_SIZE);
+	memset(d->aux, 0, RAM_SIZE);
+
+	return d;
+}
+
+/* TODO: device_ram_finish */
+
diff --git a/src/device_ram.h b/src/device_ram.h
new file mode 100644
index 0000000..5ebb54d
--- /dev/null
+++ b/src/device_ram.h
@@ -0,0 +1,8 @@
+#ifndef _DEVICE_RAM_H_
+#define _DEVICE_RAM_H_
+
+#include "device.h"
+
+device_t * device_ram_init();
+
+#endif /* _DEVICE_RAM_H_ */