diff --git a/arch/x86/kernel/apic.c b/arch/x86/kernel/apic.c
index f999e110..e134483b 100644
--- a/arch/x86/kernel/apic.c
+++ b/arch/x86/kernel/apic.c
@@ -310,10 +310,10 @@ int apic_calibration(void)
 	/* wait 3 time slices to determine a ICR */
 	start = rdtsc();
 	do {
-		//flush_pipeline();
+		flush_pipeline();
 		end = rdtsc();
 		ticks = end > start ? end - start : start - end;
-	} while(ticks < 3*RC_REFCLOCKMHZ / TIMER_FREQ);
+	} while(ticks*TIMER_FREQ < 3*RC_REFCLOCKMHZ*1000000);
 
 	diff = 0xFFFFFFFF - lapic_read(APIC_CCR);