M include/mgba/internal/ds/ds.h → include/mgba/internal/ds/ds.h

@@ -20,6 +20,7 @@ #include <mgba/internal/ds/video.h>
 
 extern const uint32_t DS_ARM946ES_FREQUENCY;
 extern const uint32_t DS_ARM7TDMI_FREQUENCY;
+extern const uint8_t DS_CHIP_ID[4];
 
 enum DSIRQ {
 	DS_IRQ_VBLANK = 0x0,

M src/ds/ds.c → src/ds/ds.c

@@ -23,6 +23,7 @@
 const uint32_t DS_ARM946ES_FREQUENCY = 0x1FF61FE;
 const uint32_t DS_ARM7TDMI_FREQUENCY = 0xFFB0FF;
 const uint32_t DS_COMPONENT_MAGIC = 0x1FF61FE;
+const uint8_t DS_CHIP_ID[4] = { 0xC2, 0x0F, 0x00, 0x00 };
 
 static const size_t DS_ROM_MAGIC_OFFSET = 0x15C;
 static const uint8_t DS_ROM_MAGIC[] = { 0x56, 0xCF };
@@ -278,6 +279,10 @@ DS7IOInit(ds);
 
 	struct DSCartridge* header = ds->romVf->map(ds->romVf, sizeof(*header), MAP_READ);
 	if (header) {
+		memcpy(&ds->memory.ram[0x3FF800 >> 2], DS_CHIP_ID, 4);
+		memcpy(&ds->memory.ram[0x3FF804 >> 2], DS_CHIP_ID, 4);
+		memcpy(&ds->memory.ram[0x3FFC00 >> 2], DS_CHIP_ID, 4);
+		memcpy(&ds->memory.ram[0x3FFC04 >> 2], DS_CHIP_ID, 4);
 		memcpy(&ds->memory.ram[0x3FFE00 >> 2], header, 0x170);
 		DS7IOWrite32(ds, DS_REG_ROMCNT_LO, header->busTiming | 0x2700000);
 		// TODO: Error check

M src/ds/slot1.c → src/ds/slot1.c

@@ -50,6 +50,10 @@ }
 		ds->memory.slot1.transferRemaining = ds->memory.slot1.transferSize;
 		DSSlot1StepTransfer(ds);
 		break;
+	case 0xB8:
+		memcpy(ds->memory.slot1.readBuffer, DS_CHIP_ID, 4);
+		ds->memory.slot1.transferRemaining = 0;
+		break;
 	default:
 		mLOG(DS_SLOT1, STUB, "Unimplemented card command: %02X%02X%02X%02X%02X%02X%02X%02X",
 		     ds->memory.slot1.command[0], ds->memory.slot1.command[1],