diff --git a/abstract-machine/am/src/platform/nemu/ioe/audio.c b/abstract-machine/am/src/platform/nemu/ioe/audio.c
index 98c2478..a3e0519 100644
--- a/abstract-machine/am/src/platform/nemu/ioe/audio.c
+++ b/abstract-machine/am/src/platform/nemu/ioe/audio.c
@@ -10,6 +10,7 @@
 
 static uint32_t audio_write = 0;
 static uint32_t audio_sbuf_size;
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
 
 void __am_audio_init() {
 }
@@ -39,16 +40,15 @@ void __am_audio_play(AM_AUDIO_PLAY_T *ctl) {
   while (cnt) {
     // lock sbuf
     outl(AUDIO_INIT_ADDR, 2);
-    for (; i < cnt; i++) {
-      if (inl(AUDIO_COUNT_ADDR) == audio_sbuf_size) {
-        i--;
-        break;
-      } else {
-        outb(AUDIO_SBUF_ADDR + audio_write, ((uint8_t*)ctl->buf.start)[i]);
-        audio_write = (audio_write + 1) % audio_sbuf_size;
-        outl(AUDIO_COUNT_ADDR, inl(AUDIO_COUNT_ADDR) + 1);
-      }
+
+    int last = audio_sbuf_size - inl(AUDIO_COUNT_ADDR);
+    int write_num = MIN(last, cnt);
+    for (int j = i; j < write_num; i ++, j ++) {
+      outb(AUDIO_SBUF_ADDR + audio_write, ((uint8_t*)(ctl->buf.start))[i]);
+      audio_write = (audio_write + 1) % audio_sbuf_size;
     }
+    cnt -= write_num;
+    outl(AUDIO_COUNT_ADDR, inl(AUDIO_COUNT_ADDR) + write_num);
     // unlock sbuf
     outl(AUDIO_INIT_ADDR, 0);
   }