diff --git a/arch/x86/boot/main.c b/arch/x86/boot/main.c
index 01aa64b..197421d 100644
--- a/arch/x86/boot/main.c
+++ b/arch/x86/boot/main.c
@@ -73,7 +73,8 @@
  */
 static void query_ist(void)
 {
-	/* Some 486 BIOSes apparently crash on this call */
+	/* Some older BIOSes apparently crash on this call, so filter
+	   it from machines too old to have SpeedStep at all. */
 	if (cpu.level < 6)
 		return;