diff --git a/libcpuid/rdtsc.c b/libcpuid/rdtsc.c
index 75c93ba..46eb26b 100644
--- a/libcpuid/rdtsc.c
+++ b/libcpuid/rdtsc.c
@@ -243,7 +243,6 @@ int cpu_clock_by_ic(int millis, int runs)
 	int max_value = 0, cur_value, i, ri, cycles_inner, cycles_outer, c;
 	struct cpu_id_t* id;
 	uint64_t t0, t1, tl, hz;
-	int num_instructions = 256;
 	int sse_multiplier = 1;
 	if (millis <= 0 || runs <= 0) return -2;
 	id = get_cached_cpuid();
@@ -279,7 +278,7 @@ int cpu_clock_by_ic(int millis, int runs)
 		} while (t1 - t0 < tl * (uint64_t) 8);
 		// cpu_Hz = cycles_inner * cycles_outer * 256 / (t1 - t0) * 1000000
 		debugf(2, "c = %d, td = %llu\n", c, t1 - t0);
-		hz = ((uint64_t) cycles_inner * (uint64_t) num_instructions + 8) * 
+		hz = ((uint64_t) cycles_inner * (uint64_t) 256 + 12) * 
 		     (uint64_t) cycles_outer * (uint64_t) sse_multiplier * (uint64_t) c * (uint64_t) 1000000
 		     / (t1 - t0);
 		cur_value = (int) (hz / 1000000);