diff --git a/tools/power/x86/intel-speed-select/isst-config.c b/tools/power/x86/intel-speed-select/isst-config.c
index b8f4846d7c786c7fc7672f02957101c032276a44..c773c6cc02a5d5e8492accaf12a4bc89afd80fb2 100644
--- a/tools/power/x86/intel-speed-select/isst-config.c
+++ b/tools/power/x86/intel-speed-select/isst-config.c
@@ -316,10 +316,24 @@ static void set_max_cpu_num(void)
 {
 	FILE *filep;
 	unsigned long dummy;
+	int i;
 
 	topo_max_cpus = 0;
-	filep = fopen_or_exit(
-		"/sys/devices/system/cpu/cpu0/topology/thread_siblings", "r");
+	for (i = 0; i < 256; ++i) {
+		char path[256];
+
+		snprintf(path, sizeof(path),
+			 "/sys/devices/system/cpu/cpu%d/topology/thread_siblings", i);
+		filep = fopen(path, "r");
+		if (filep)
+			break;
+	}
+
+	if (!filep) {
+		fprintf(stderr, "Can't get max cpu number\n");
+		exit(0);
+	}
+
 	while (fscanf(filep, "%lx,", &dummy) == 1)
 		topo_max_cpus += BITMASK_SIZE;
 	fclose(filep);