diff --git a/src/xenia/kernel/objects/xtimer.cc b/src/xenia/kernel/objects/xtimer.cc
index 988fe6d6d..63f2bf17a 100644
--- a/src/xenia/kernel/objects/xtimer.cc
+++ b/src/xenia/kernel/objects/xtimer.cc
@@ -9,6 +9,8 @@
 
 #include <xenia/kernel/objects/xtimer.h>
 
+#include <xenia/cpu/processor.h>
+
 
 using namespace xe;
 using namespace xe::kernel;
@@ -44,14 +46,36 @@ void XTimer::Initialize(uint32_t timer_type) {
   handle_ = CreateWaitableTimer(NULL, manual_reset, NULL);
 }
 
-X_STATUS XTimer::SetTimer(int64_t due_time, uint32_t period_ms) {
+X_STATUS XTimer::SetTimer(
+    int64_t due_time, uint32_t period_ms,
+    uint32_t routine, uint32_t routine_arg, bool resume) {
+  // Stash routine for callback.
+  current_routine_ = routine;
+  current_routine_arg_ = routine_arg;
+
   LARGE_INTEGER due_time_li;
   due_time_li.QuadPart = due_time;
-  if (SetWaitableTimer(handle_, &due_time_li, period_ms, NULL, NULL, TRUE)) {
-    return X_STATUS_SUCCESS;
-  } else {
-    return X_STATUS_UNSUCCESSFUL;
+  BOOL result = SetWaitableTimer(
+      handle_, &due_time_li, period_ms,
+      routine ? (PTIMERAPCROUTINE)CompletionRoutine : NULL, this,
+      resume ? TRUE : FALSE);
+
+  // Caller is checking for STATUS_TIMER_RESUME_IGNORED.
+  // This occurs if result == TRUE but error is set.
+  if (!result && GetLastError() == ERROR_NOT_SUPPORTED) {
+    return X_STATUS_TIMER_RESUME_IGNORED;
   }
+
+  return result ? X_STATUS_SUCCESS : X_STATUS_UNSUCCESSFUL;
+}
+
+void XTimer::CompletionRoutine(
+    XTimer* timer, DWORD timer_low, DWORD timer_high) {
+  XEASSERT(timer->current_routine_);
+
+  // Queue APC to call back routine with (arg, low, high).
+  // TODO(benvanik): APC dispatch.
+  XELOGE("Timer needs APC!");
 }
 
 X_STATUS XTimer::Cancel() {
diff --git a/src/xenia/kernel/objects/xtimer.h b/src/xenia/kernel/objects/xtimer.h
index d25774b22..586c45e41 100644
--- a/src/xenia/kernel/objects/xtimer.h
+++ b/src/xenia/kernel/objects/xtimer.h
@@ -27,13 +27,20 @@ public:
   void Initialize(uint32_t timer_type);
 
   // completion routine, arg to completion routine
-  X_STATUS SetTimer(int64_t due_time, uint32_t period_ms);
+  X_STATUS SetTimer(int64_t due_time, uint32_t period_ms,
+                    uint32_t routine, uint32_t routine_arg, bool resume);
   X_STATUS Cancel();
 
   virtual void* GetWaitHandle() { return handle_; }
 
 private:
   HANDLE handle_;
+
+  uint32_t current_routine_;
+  uint32_t current_routine_arg_;
+
+  static void CompletionRoutine(
+      XTimer* timer, DWORD timer_low, DWORD timer_high);
 };
 
 
diff --git a/src/xenia/kernel/xboxkrnl_debug.cc b/src/xenia/kernel/xboxkrnl_debug.cc
index bd3e25615..8127d45b0 100644
--- a/src/xenia/kernel/xboxkrnl_debug.cc
+++ b/src/xenia/kernel/xboxkrnl_debug.cc
@@ -282,7 +282,7 @@ SHIM_CALL RtlRaiseException_shim(
 
   // TODO(benvanik): unwinding.
   // This is going to suck.
-  XEASSERTALWAYS();
+  DebugBreak();
 }
 
 
diff --git a/src/xenia/kernel/xboxkrnl_threading.cc b/src/xenia/kernel/xboxkrnl_threading.cc
index 39bf3abba..fae066aea 100644
--- a/src/xenia/kernel/xboxkrnl_threading.cc
+++ b/src/xenia/kernel/xboxkrnl_threading.cc
@@ -977,24 +977,23 @@ SHIM_CALL NtCreateTimer_shim(
 SHIM_CALL NtSetTimerEx_shim(
     PPCContext* ppc_state, KernelState* state) {
   uint32_t timer_handle = SHIM_GET_ARG_32(0);
-  uint32_t info_class = SHIM_GET_ARG_32(1);
-  uint32_t info_ptr = SHIM_GET_ARG_32(2);
-  uint32_t info_length = SHIM_GET_ARG_32(3);
+  uint32_t due_time_ptr = SHIM_GET_ARG_32(1);
+  uint32_t routine = SHIM_GET_ARG_32(2); // PTIMERAPCROUTINE
+  uint32_t unk_one = SHIM_GET_ARG_32(3);
+  uint32_t routine_arg = SHIM_GET_ARG_32(4);
+  uint32_t resume = SHIM_GET_ARG_32(5);
+  uint32_t period_ms = SHIM_GET_ARG_32(6);
+  uint32_t unk_zero = SHIM_GET_ARG_32(7);
 
-  // UNVERIFIED
-  XEASSERTALWAYS();
+  XEASSERT(unk_one == 1);
+  XEASSERT(unk_zero == 0);
+
+  uint64_t due_time = SHIM_MEM_64(due_time_ptr);
 
   XELOGD(
-      "NtSetTimerEx(%.8X, %.8X, %.8X, %d)",
-      timer_handle, info_class, info_ptr, info_length);
-
-  // TIMER_BASIC_INFORMATION
-  XEASSERT(info_class == 0);
-  XEASSERT(info_length == 12);
-
-  uint64_t due_time = SHIM_MEM_64(info_ptr + 0);
-  uint32_t timer_state = SHIM_MEM_32(info_ptr + 8); // unused?
-  uint32_t period_ms = 0; // Not repeating.
+      "NtSetTimerEx(%.8X, %.8X(%lld), %.8X, %.8X, %.8X, %.1X, %d, %.8X)",
+      timer_handle, due_time_ptr, due_time, routine, unk_one,
+      routine_arg, resume, period_ms, unk_zero);
 
   X_STATUS result = X_STATUS_SUCCESS;
 
@@ -1002,7 +1001,8 @@ SHIM_CALL NtSetTimerEx_shim(
   result = state->object_table()->GetObject(
       timer_handle, (XObject**)&timer);
   if (XSUCCEEDED(result)) {
-    result = timer->SetTimer(due_time, period_ms);
+    result = timer->SetTimer(
+        due_time, period_ms, routine, routine_arg, resume ? true : false);
     timer->Release();
   }
 
@@ -1016,7 +1016,7 @@ SHIM_CALL NtCancelTimer_shim(
   uint32_t current_state_ptr = SHIM_GET_ARG_32(1);
 
   // UNVERIFIED
-  XEASSERTALWAYS();
+  DebugBreak();
 
   XELOGD(
       "NtCancelTimer(%.8X, %.8X)",
diff --git a/src/xenia/xbox.h b/src/xenia/xbox.h
index fa622ebb8..837e5dc89 100644
--- a/src/xenia/xbox.h
+++ b/src/xenia/xbox.h
@@ -33,6 +33,7 @@ typedef uint32_t X_STATUS;
 #define X_STATUS_ALERTED                                ((X_STATUS)0x00000101L)
 #define X_STATUS_TIMEOUT                                ((X_STATUS)0x00000102L)
 #define X_STATUS_PENDING                                ((X_STATUS)0x00000103L)
+#define X_STATUS_TIMER_RESUME_IGNORED                   ((X_STATUS)0x40000025L)
 #define X_STATUS_UNSUCCESSFUL                           ((X_STATUS)0xC0000001L)
 #define X_STATUS_NOT_IMPLEMENTED                        ((X_STATUS)0xC0000002L)
 #define X_STATUS_INFO_LENGTH_MISMATCH                   ((X_STATUS)0xC0000004L)