diff --git a/src/arm/arm.c b/src/arm/arm.c
index 16aaca579..e1e153d94 100644
--- a/src/arm/arm.c
+++ b/src/arm/arm.c
@@ -320,6 +320,28 @@ void ARMRunLoop(struct ARMCore* cpu) {
 	cpu->irqh.processEvents(cpu);
 }
 
+int32_t ARMRunCycles(struct ARMCore* cpu, int32_t cycles) {
+	int32_t startCycles = cpu->cycles;
+	int32_t endCycles = startCycles + cycles;
+
+	if (cpu->executionMode == MODE_THUMB) {
+		while (cpu->cycles < cpu->nextEvent && cpu->cycles < endCycles) {
+			ThumbStep(cpu);
+		}
+	} else {
+		while (cpu->cycles < cpu->nextEvent && cpu->cycles < endCycles) {
+			ARMStep(cpu);
+		}
+	}
+
+	endCycles = cpu->cycles - startCycles;
+	if (cpu->cycles >= cpu->nextEvent) {
+		// TODO: Handle HALT
+		cpu->irqh.processEvents(cpu);
+	}
+	return endCycles;
+}
+
 void ARMRunFake(struct ARMCore* cpu, uint32_t opcode) {
 	if (cpu->executionMode == MODE_ARM) {
 		cpu->gprs[ARM_PC] -= WORD_SIZE_ARM;
diff --git a/src/arm/arm.h b/src/arm/arm.h
index 803581636..5a0a518af 100644
--- a/src/arm/arm.h
+++ b/src/arm/arm.h
@@ -255,6 +255,7 @@ void ARMRaiseUndefined(struct ARMCore*);
 
 void ARMRun(struct ARMCore* cpu);
 void ARMRunLoop(struct ARMCore* cpu);
+int32_t ARMRunCycles(struct ARMCore* cpu, int32_t cycles);
 void ARMRunFake(struct ARMCore* cpu, uint32_t opcode);
 
 #endif
diff --git a/src/ds/core.c b/src/ds/core.c
index 3882ae440..b2ae25798 100644
--- a/src/ds/core.c
+++ b/src/ds/core.c
@@ -18,10 +18,12 @@
 struct DSCore {
 	struct mCore d;
 	struct ARMCore* arm7;
+	struct ARMCore* arm9;
 	int keys;
 	struct mCPUComponent* components[CPU_COMPONENT_MAX];
 	struct mDebuggerPlatform* debuggerPlatform;
 	struct mCheatDevice* cheatDevice;
+	int32_t cycleDrift;
 };
 
 static bool _DSCoreInit(struct mCore* core) {
@@ -36,12 +38,14 @@ static bool _DSCoreInit(struct mCore* core) {
 		free(ds);
 		return false;
 	}
-	core->cpu = arm9;
+	core->cpu = arm7;
 	core->board = ds;
 	core->debugger = NULL;
 	dscore->arm7 = arm7;
+	dscore->arm9 = arm9;
 	dscore->debuggerPlatform = NULL;
 	dscore->cheatDevice = NULL;
+	dscore->cycleDrift = 0;
 
 	DSCreate(ds);
 	memset(dscore->components, 0, sizeof(dscore->components));
@@ -62,11 +66,11 @@ static bool _DSCoreInit(struct mCore* core) {
 
 static void _DSCoreDeinit(struct mCore* core) {
 	struct DSCore* dscore = (struct DSCore*) core;
-	ARMDeinit(core->cpu);
 	ARMDeinit(dscore->arm7);
+	ARMDeinit(dscore->arm9);
 	DSDestroy(core->board);
-	mappedMemoryFree(core->cpu, sizeof(struct ARMCore));
 	mappedMemoryFree(dscore->arm7, sizeof(struct ARMCore));
+	mappedMemoryFree(dscore->arm9, sizeof(struct ARMCore));
 	mappedMemoryFree(core->board, sizeof(struct DS));
 #if !defined(MINIMAL_CORE) || MINIMAL_CORE < 2
 	mDirectorySetDeinit(&core->dirs);
@@ -156,19 +160,33 @@ static void _DSCoreReset(struct mCore* core) {
 }
 
 static void _DSCoreRunFrame(struct mCore* core) {
+	struct DSCore* dscore = (struct DSCore*) core;
 	struct DS* ds = core->board;
 	int32_t frameCounter = ds->video.frameCounter;
 	while (ds->video.frameCounter == frameCounter) {
-		ARMRunLoop(core->cpu);
+		dscore->cycleDrift += ARMRunCycles(dscore->arm9, 2048);
+		dscore->cycleDrift -= ARMRunCycles(dscore->arm7, dscore->cycleDrift >> 1) << 1;
 	}
 }
 
 static void _DSCoreRunLoop(struct mCore* core) {
-	ARMRunLoop(core->cpu);
+	struct DSCore* dscore = (struct DSCore*) core;
+	dscore->cycleDrift += ARMRunCycles(dscore->arm9, 2048);
+	dscore->cycleDrift -= ARMRunCycles(dscore->arm7, dscore->cycleDrift >> 1) << 1;
 }
 
 static void _DSCoreStep(struct mCore* core) {
-	ARMRun(core->cpu);
+	struct DSCore* dscore = (struct DSCore*) core;
+	int32_t runCycles;
+	if (core->cpu == dscore->arm9) {
+		runCycles = 1;
+	} else {
+		runCycles = 2;
+	}
+	dscore->cycleDrift += ARMRunCycles(dscore->arm9, runCycles);
+	if (dscore->cycleDrift > 1) {
+		dscore->cycleDrift -= ARMRunCycles(dscore->arm7, 1) << 1;
+	}
 }
 
 static size_t _DSCoreStateSize(struct mCore* core) {
@@ -325,6 +343,9 @@ static void _DSCoreAttachDebugger(struct mCore* core, struct mDebugger* debugger
 		DSDetachDebugger(core->board);
 	}
 	DSAttachDebugger(core->board, debugger);
+	struct ARMCore* cpu = core->cpu;
+	cpu->components[CPU_COMPONENT_DEBUGGER] = &debugger->d;
+	ARMHotplugAttach(cpu, CPU_COMPONENT_DEBUGGER);
 	core->debugger = debugger;
 }
 
diff --git a/src/ds/ds.c b/src/ds/ds.c
index 72217cf25..80271420f 100644
--- a/src/ds/ds.c
+++ b/src/ds/ds.c
@@ -213,13 +213,8 @@ static void DSProcessEvents(struct ARMCore* cpu) {
 
 void DSAttachDebugger(struct DS* ds, struct mDebugger* debugger) {
 	ds->debugger = (struct ARMDebugger*) debugger->platform;
-	ds->arm7->components[CPU_COMPONENT_DEBUGGER] = &debugger->d;
-	ds->arm9->components[CPU_COMPONENT_DEBUGGER] = &debugger->d;
-	ARMHotplugAttach(ds->arm7, CPU_COMPONENT_DEBUGGER);
-	ARMHotplugAttach(ds->arm9, CPU_COMPONENT_DEBUGGER);
 }
 
-
 void DSDetachDebugger(struct DS* ds) {
 	ds->debugger = NULL;
 	ARMHotplugDetach(ds->arm7, CPU_COMPONENT_DEBUGGER);