diff --git a/source/mijin/util/os.cpp b/source/mijin/util/os.cpp
index 54add49..6f82bae 100644
--- a/source/mijin/util/os.cpp
+++ b/source/mijin/util/os.cpp
@@ -39,9 +39,9 @@ namespace mijin
 // internal variables
 //
 
-#if MIJIN_TARGET_OS == MIJIN_OS_LINUX
 namespace
 {
+#if MIJIN_TARGET_OS == MIJIN_OS_LINUX
 std::mutex gDlErrorMutex; // dlerror may not be thread-safe
 
 const std::uint64_t gCPUClockResolution = []()
@@ -52,8 +52,16 @@ const std::uint64_t gCPUClockResolution = []()
     MIJIN_ASSERT(time.tv_sec == 0, "What kind of cpu clock is this?");
     return static_cast<std::uint64_t>(time.tv_nsec);
 }();
-};
-#endif // MIJIN_TARGET_OS == MIJIN_OS_LINUX
+#elif MIJIN_TARGET_OS == MIJIN_OS_WINDOWS
+const std::uint64_t gCPUTickFrequency = []()
+{
+    LARGE_INTEGER ticks;
+    [[maybe_unused]] const BOOL result = QueryPerformanceFrequency(&ticks);
+    MIJIN_ASSERT(result, "Error getting cpu frequency.");
+    return static_cast<std::uint64_t>(ticks.QuadPart);
+}();
+#endif // MIJIN_TARGET_OS == MIJIN_OS_LINUX || MIJIN_TARGET_OS == MIJIN_OS_WINDOWS
+}
 
 //
 // internal functions
@@ -196,8 +204,10 @@ std::uint64_t getCPUTicks() MIJIN_NOEXCEPT
     MIJIN_ASSERT(result == 0, "Error getting cpu time.");
     return (static_cast<std::uint64_t>(time.tv_sec) * 1e9 + time.tv_nsec) / gCPUClockResolution;
 #else
-    MIJIN_ERROR("TODO");
-    return 0;
+    LARGE_INTEGER ticks;
+    [[maybe_unused]] const BOOL result = QueryPerformanceCounter(&ticks);
+    MIJIN_ASSERT(result, "Error getting cpu time.");
+    return static_cast<std::uint64_t>(ticks.QuadPart);
 #endif
 }
 
@@ -206,8 +216,7 @@ std::uint64_t getCPUTicksPerSecond() MIJIN_NOEXCEPT
 #if MIJIN_TARGET_OS == MIJIN_OS_LINUX
     return 1e9 / gCPUClockResolution;
 #else
-    MIJIN_ERROR("TODO");
-    return 0;
+    return gCPUTickFrequency;
 #endif
 }
 } // namespace mijin