diff --git a/src/gba.c b/src/gba.c
index 82eb80a4b..fc42574c0 100644
--- a/src/gba.c
+++ b/src/gba.c
@@ -1,6 +1,7 @@
 #include "gba.h"
 
 #include <sys/mman.h>
+#include <unistd.h>
 
 static const char* GBA_CANNOT_MMAP = "Could not map memory";
 
@@ -12,6 +13,7 @@ void GBAInit(struct GBA* gba) {
 
 	gba->memory.p = gba;
 	GBAMemoryInit(&gba->memory);
+	ARMAssociateMemory(&gba->cpu, &gba->memory.d);
 }
 
 void GBADeinit(struct GBA* gba) {
@@ -45,32 +47,37 @@ void GBAMemoryDeinit(struct GBAMemory* memory) {
 	munmap(memory->iwram, SIZE_WORKING_IRAM);
 }
 
+void GBALoadROM(struct GBA* gba, int fd) {
+	gba->memory.rom = mmap(0, SIZE_CART0, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FILE, fd, 0);
+	// TODO: error check
+}
+
 int32_t GBALoad32(struct ARMMemory* memory, uint32_t address) {
 	struct GBAMemory* gbaMemory = (struct GBAMemory*) memory;
 
-	switch (address & OFFSET_MASK) {
-	case REGION_BIOS:
+	switch (address & ~OFFSET_MASK) {
+	case BASE_BIOS:
 		break;
-	case REGION_WORKING_RAM:
+	case BASE_WORKING_RAM:
 		break;
-	case REGION_WORKING_IRAM:
+	case BASE_WORKING_IRAM:
 		break;
-	case REGION_IO:
+	case BASE_IO:
 		break;
-	case REGION_PALETTE_RAM:
+	case BASE_PALETTE_RAM:
 		break;
-	case REGION_VRAM:
+	case BASE_VRAM:
 		break;
-	case REGION_OAM:
+	case BASE_OAM:
 		break;
-	case REGION_CART0:
-	case REGION_CART0_EX:
-	case REGION_CART1:
-	case REGION_CART1_EX:
-	case REGION_CART2:
-	case REGION_CART2_EX:
-		break;
-	case REGION_CART_SRAM:
+	case BASE_CART0:
+	case BASE_CART0_EX:
+	case BASE_CART1:
+	case BASE_CART1_EX:
+	case BASE_CART2:
+	case BASE_CART2_EX:
+		return gbaMemory->rom[(address & (SIZE_CART0 - 1)) >> 2];
+	case BASE_CART_SRAM:
 		break;
 	default:
 		break;
@@ -82,29 +89,29 @@ int32_t GBALoad32(struct ARMMemory* memory, uint32_t address) {
 int16_t GBALoad16(struct ARMMemory* memory, uint32_t address) {
 	struct GBAMemory* gbaMemory = (struct GBAMemory*) memory;
 
-	switch (address & OFFSET_MASK) {
-	case REGION_BIOS:
+	switch (address & ~OFFSET_MASK) {
+	case BASE_BIOS:
 		break;
-	case REGION_WORKING_RAM:
+	case BASE_WORKING_RAM:
 		break;
-	case REGION_WORKING_IRAM:
+	case BASE_WORKING_IRAM:
 		break;
-	case REGION_IO:
+	case BASE_IO:
 		break;
-	case REGION_PALETTE_RAM:
+	case BASE_PALETTE_RAM:
 		break;
-	case REGION_VRAM:
+	case BASE_VRAM:
 		break;
-	case REGION_OAM:
+	case BASE_OAM:
 		break;
-	case REGION_CART0:
-	case REGION_CART0_EX:
-	case REGION_CART1:
-	case REGION_CART1_EX:
-	case REGION_CART2:
-	case REGION_CART2_EX:
+	case BASE_CART0:
+	case BASE_CART0_EX:
+	case BASE_CART1:
+	case BASE_CART1_EX:
+	case BASE_CART2:
+	case BASE_CART2_EX:
 		break;
-	case REGION_CART_SRAM:
+	case BASE_CART_SRAM:
 		break;
 	default:
 		break;
@@ -116,29 +123,29 @@ int16_t GBALoad16(struct ARMMemory* memory, uint32_t address) {
 uint16_t GBALoadU16(struct ARMMemory* memory, uint32_t address) {
 	struct GBAMemory* gbaMemory = (struct GBAMemory*) memory;
 
-	switch (address & OFFSET_MASK) {
-	case REGION_BIOS:
+	switch (address & ~OFFSET_MASK) {
+	case BASE_BIOS:
 		break;
-	case REGION_WORKING_RAM:
+	case BASE_WORKING_RAM:
 		break;
-	case REGION_WORKING_IRAM:
+	case BASE_WORKING_IRAM:
 		break;
-	case REGION_IO:
+	case BASE_IO:
 		break;
-	case REGION_PALETTE_RAM:
+	case BASE_PALETTE_RAM:
 		break;
-	case REGION_VRAM:
+	case BASE_VRAM:
 		break;
-	case REGION_OAM:
+	case BASE_OAM:
 		break;
-	case REGION_CART0:
-	case REGION_CART0_EX:
-	case REGION_CART1:
-	case REGION_CART1_EX:
-	case REGION_CART2:
-	case REGION_CART2_EX:
+	case BASE_CART0:
+	case BASE_CART0_EX:
+	case BASE_CART1:
+	case BASE_CART1_EX:
+	case BASE_CART2:
+	case BASE_CART2_EX:
 		break;
-	case REGION_CART_SRAM:
+	case BASE_CART_SRAM:
 		break;
 	default:
 		break;
@@ -150,29 +157,29 @@ uint16_t GBALoadU16(struct ARMMemory* memory, uint32_t address) {
 int8_t GBALoad8(struct ARMMemory* memory, uint32_t address) {
 	struct GBAMemory* gbaMemory = (struct GBAMemory*) memory;
 
-	switch (address & OFFSET_MASK) {
-	case REGION_BIOS:
+	switch (address & ~OFFSET_MASK) {
+	case BASE_BIOS:
 		break;
-	case REGION_WORKING_RAM:
+	case BASE_WORKING_RAM:
 		break;
-	case REGION_WORKING_IRAM:
+	case BASE_WORKING_IRAM:
 		break;
-	case REGION_IO:
+	case BASE_IO:
 		break;
-	case REGION_PALETTE_RAM:
+	case BASE_PALETTE_RAM:
 		break;
-	case REGION_VRAM:
+	case BASE_VRAM:
 		break;
-	case REGION_OAM:
+	case BASE_OAM:
 		break;
-	case REGION_CART0:
-	case REGION_CART0_EX:
-	case REGION_CART1:
-	case REGION_CART1_EX:
-	case REGION_CART2:
-	case REGION_CART2_EX:
+	case BASE_CART0:
+	case BASE_CART0_EX:
+	case BASE_CART1:
+	case BASE_CART1_EX:
+	case BASE_CART2:
+	case BASE_CART2_EX:
 		break;
-	case REGION_CART_SRAM:
+	case BASE_CART_SRAM:
 		break;
 	default:
 		break;
@@ -184,29 +191,29 @@ int8_t GBALoad8(struct ARMMemory* memory, uint32_t address) {
 uint8_t GBALoadU8(struct ARMMemory* memory, uint32_t address) {
 	struct GBAMemory* gbaMemory = (struct GBAMemory*) memory;
 
-	switch (address & OFFSET_MASK) {
-	case REGION_BIOS:
+	switch (address & ~OFFSET_MASK) {
+	case BASE_BIOS:
 		break;
-	case REGION_WORKING_RAM:
+	case BASE_WORKING_RAM:
 		break;
-	case REGION_WORKING_IRAM:
+	case BASE_WORKING_IRAM:
 		break;
-	case REGION_IO:
+	case BASE_IO:
 		break;
-	case REGION_PALETTE_RAM:
+	case BASE_PALETTE_RAM:
 		break;
-	case REGION_VRAM:
+	case BASE_VRAM:
 		break;
-	case REGION_OAM:
+	case BASE_OAM:
 		break;
-	case REGION_CART0:
-	case REGION_CART0_EX:
-	case REGION_CART1:
-	case REGION_CART1_EX:
-	case REGION_CART2:
-	case REGION_CART2_EX:
+	case BASE_CART0:
+	case BASE_CART0_EX:
+	case BASE_CART1:
+	case BASE_CART1_EX:
+	case BASE_CART2:
+	case BASE_CART2_EX:
 		break;
-	case REGION_CART_SRAM:
+	case BASE_CART_SRAM:
 		break;
 	default:
 		break;
@@ -218,24 +225,24 @@ uint8_t GBALoadU8(struct ARMMemory* memory, uint32_t address) {
 void GBAStore32(struct ARMMemory* memory, uint32_t address, int32_t value) {
 	struct GBAMemory* gbaMemory = (struct GBAMemory*) memory;
 
-	switch (address & OFFSET_MASK) {
-	case REGION_WORKING_RAM:
+	switch (address & ~OFFSET_MASK) {
+	case BASE_WORKING_RAM:
 		break;
-	case REGION_WORKING_IRAM:
+	case BASE_WORKING_IRAM:
 		break;
-	case REGION_IO:
+	case BASE_IO:
 		break;
-	case REGION_PALETTE_RAM:
+	case BASE_PALETTE_RAM:
 		break;
-	case REGION_VRAM:
+	case BASE_VRAM:
 		break;
-	case REGION_OAM:
+	case BASE_OAM:
 		break;
-	case REGION_CART0:
+	case BASE_CART0:
 		break;
-	case REGION_CART2_EX:
+	case BASE_CART2_EX:
 		break;
-	case REGION_CART_SRAM:
+	case BASE_CART_SRAM:
 		break;
 	default:
 		break;
@@ -245,24 +252,24 @@ void GBAStore32(struct ARMMemory* memory, uint32_t address, int32_t value) {
 void GBAStore16(struct ARMMemory* memory, uint32_t address, int16_t value) {
 	struct GBAMemory* gbaMemory = (struct GBAMemory*) memory;
 
-	switch (address & OFFSET_MASK) {
-	case REGION_WORKING_RAM:
+	switch (address & ~OFFSET_MASK) {
+	case BASE_WORKING_RAM:
 		break;
-	case REGION_WORKING_IRAM:
+	case BASE_WORKING_IRAM:
 		break;
-	case REGION_IO:
+	case BASE_IO:
 		break;
-	case REGION_PALETTE_RAM:
+	case BASE_PALETTE_RAM:
 		break;
-	case REGION_VRAM:
+	case BASE_VRAM:
 		break;
-	case REGION_OAM:
+	case BASE_OAM:
 		break;
-	case REGION_CART0:
+	case BASE_CART0:
 		break;
-	case REGION_CART2_EX:
+	case BASE_CART2_EX:
 		break;
-	case REGION_CART_SRAM:
+	case BASE_CART_SRAM:
 		break;
 	default:
 		break;
@@ -272,26 +279,26 @@ void GBAStore16(struct ARMMemory* memory, uint32_t address, int16_t value) {
 void GBAStore8(struct ARMMemory* memory, uint32_t address, int8_t value) {
 	struct GBAMemory* gbaMemory = (struct GBAMemory*) memory;
 
-	switch (address & OFFSET_MASK) {
-	case REGION_WORKING_RAM:
+	switch (address & ~OFFSET_MASK) {
+	case BASE_WORKING_RAM:
 		break;
-	case REGION_WORKING_IRAM:
+	case BASE_WORKING_IRAM:
 		break;
-	case REGION_IO:
+	case BASE_IO:
 		break;
-	case REGION_PALETTE_RAM:
+	case BASE_PALETTE_RAM:
 		break;
-	case REGION_VRAM:
+	case BASE_VRAM:
 		break;
-	case REGION_OAM:
+	case BASE_OAM:
 		break;
-	case REGION_CART0:
+	case BASE_CART0:
 		break;
-	case REGION_CART2_EX:
+	case BASE_CART2_EX:
 		break;
-	case REGION_CART_SRAM:
+	case BASE_CART_SRAM:
 		break;
 	default:
 		break;
 	}
-}
\ No newline at end of file
+}
diff --git a/src/gba.h b/src/gba.h
index 65c42bd98..0f8cc9830 100644
--- a/src/gba.h
+++ b/src/gba.h
@@ -25,6 +25,22 @@ enum GBAMemoryRegion {
 	REGION_CART_SRAM = 0xE
 };
 
+enum GBAMemoryBase {
+	BASE_BIOS = 0x00000000,
+	BASE_WORKING_RAM = 0x02000000,
+	BASE_WORKING_IRAM = 0x03000000,
+	BASE_IO = 0x04000000,
+	BASE_PALETTE_RAM = 0x05000000,
+	BASE_VRAM = 0x06000000,
+	BASE_OAM = 0x07000000,
+	BASE_CART0 = 0x08000000,
+	BASE_CART0_EX = 0x09000000,
+	BASE_CART1 = 0x0A000000,
+	BASE_CART1_EX = 0x0B000000,
+	BASE_CART2 = 0x0C000000,
+	BASE_CART2_EX = 0x0D000000,
+	BASE_CART_SRAM = 0x0E000000
+};
 enum {
 	SIZE_BIOS = 0x00004000,
 	SIZE_WORKING_RAM = 0x00040000,
@@ -75,6 +91,8 @@ void GBADeinit(struct GBA* gba);
 void GBAMemoryInit(struct GBAMemory* memory);
 void GBAMemoryDeinit(struct GBAMemory* memory);
 
+void GBALoadROM(struct GBA* gba, int fd);
+
 int32_t GBALoad32(struct ARMMemory* memory, uint32_t address);
 int16_t GBALoad16(struct ARMMemory* memory, uint32_t address);
 uint16_t GBALoadU16(struct ARMMemory* memory, uint32_t address);
@@ -85,4 +103,4 @@ void GBAStore32(struct ARMMemory* memory, uint32_t address, int32_t value);
 void GBAStore16(struct ARMMemory* memory, uint32_t address, int16_t value);
 void GBAStore8(struct ARMMemory* memory, uint32_t address, int8_t value);
 
-#endif
\ No newline at end of file
+#endif