diff --git a/TESTS/events/queue/main.cpp b/TESTS/events/queue/main.cpp
index dc45b7ed08..1b03793adf 100644
--- a/TESTS/events/queue/main.cpp
+++ b/TESTS/events/queue/main.cpp
@@ -34,6 +34,16 @@ using namespace utest::v1;
 // (for more details about EVENTS_EVENT_SIZE see EventQueue constructor)
 #define TEST_EQUEUE_SIZE (18*EVENTS_EVENT_SIZE)
 
+// By empirical, we take 80MHz CPU/2ms delay as base tolerance for time left test.
+// For higher CPU frequency, tolerance is fixed to 2ms.
+// For lower CPU frequency, tolerance is inversely proportional to CPU frequency.
+// E.g.:
+// 100MHz: 2ms
+// 80MHz: 2ms
+// 64MHz: 3ms
+// 48MHz: 4ms
+#define ALLOWED_TIME_LEFT_TOLERANCE_MS   ((SystemCoreClock >= 80000000) ? 2 : ((80000000 * 2 + SystemCoreClock - 1) / SystemCoreClock))
+
 // flag for called
 volatile bool touched = false;
 
@@ -283,7 +293,7 @@ int timeleft_events[2];
 void check_time_left(EventQueue *queue, int index, int expected)
 {
     const int event_id = timeleft_events[index];
-    TEST_ASSERT_INT_WITHIN(2, expected, queue->time_left(event_id));
+    TEST_ASSERT_INT_WITHIN(ALLOWED_TIME_LEFT_TOLERANCE_MS, expected, queue->time_left(event_id));
     touched = true;
 }
 
diff --git a/TESTS/mbed_hal/stack_size_unification/main.cpp b/TESTS/mbed_hal/stack_size_unification/main.cpp
index 3707727a4a..f6d634fd43 100644
--- a/TESTS/mbed_hal/stack_size_unification/main.cpp
+++ b/TESTS/mbed_hal/stack_size_unification/main.cpp
@@ -40,7 +40,7 @@ extern uint32_t mbed_stack_isr_size;
 #define EXPECTED_ISR_STACK_SIZE                  (1024)
 #endif
 
-#if defined(TARGET_NUCLEO_F070RB) || defined(TARGET_NANO100) || defined(TARGET_STM32F072RB) || defined(TARGET_TMPM46B) || defined(TARGET_TMPM066)
+#if defined(TARGET_NUCLEO_F070RB) || defined(TARGET_STM32F072RB) || defined(TARGET_TMPM46B) || defined(TARGET_TMPM066)
 #define EXPECTED_MAIN_THREAD_STACK_SIZE          (3072)
 #else
 #define EXPECTED_MAIN_THREAD_STACK_SIZE          (4096)
diff --git a/targets/TARGET_NUVOTON/TARGET_NANO100/device/StdDriver/nano100_clk.c b/targets/TARGET_NUVOTON/TARGET_NANO100/device/StdDriver/nano100_clk.c
index 16bcab302d..3f763078b0 100644
--- a/targets/TARGET_NUVOTON/TARGET_NANO100/device/StdDriver/nano100_clk.c
+++ b/targets/TARGET_NUVOTON/TARGET_NANO100/device/StdDriver/nano100_clk.c
@@ -613,7 +613,7 @@ uint32_t CLK_WaitClockReady(uint32_t u32ClkMask)
 {
     int32_t i32TimeOutCnt;
 
-    i32TimeOutCnt = __HSI / 200; /* About 5ms */
+    i32TimeOutCnt = __HSI / 20; /* About 50ms */
 
     while((CLK->CLKSTATUS & u32ClkMask) != u32ClkMask) {
         if(i32TimeOutCnt-- <= 0)