diff --git a/nemu/src/device/timer.c b/nemu/src/device/timer.c
index 2aff819..27e4e01 100644
--- a/nemu/src/device/timer.c
+++ b/nemu/src/device/timer.c
@@ -23,6 +23,7 @@ static void rtc_io_handler(uint32_t offset, int len, bool is_write) {
   assert(offset == 0 || offset == 4);
   if (!is_write && offset == 4) {
     uint64_t us = get_time();
+    printf("rtc_io_handle %ld\n", us);
     rtc_port_base[0] = (uint32_t)us;
     rtc_port_base[1] = us >> 32;
   }