diff -urp a/init/calibrate.c b/init/calibrate.c
--- a/init/calibrate.c	2006-10-02 11:39:32.000000000 -0400
+++ b/init/calibrate.c	2007-01-27 16:39:35.000000000 -0500
@@ -1,5 +1,7 @@
 /* calibrate.c: default delay calibration
  *
+ * vim:sw=8 noet
+ *
  * Excised from init/main.c
  *  Copyright (C) 1991, 1992  Linus Torvalds
  */
@@ -7,9 +9,36 @@
 #include <linux/sched.h>
 #include <linux/delay.h>
 #include <linux/init.h>
+#include <linux/dmi.h>
+#include <asm/io.h>
 
 #include <asm/timex.h>
 
+/* On Macbook we have trouble calibrating the delay loop due to excessive
+ * latency in the system management interrupt.  We fix this problem by
+ * disabling the "legacy USB" function of the SMC during delay loop
+ * calibration.  From Intel ICH7 manual, this is bit 3 of SMI_EN register
+ * located at 0x430.
+ */
+static int __initdata macbook_calibrate_quirk;
+
+static int __init init_macbook_calibrate_quirk (struct dmi_system_id *d)
+{
+	printk(KERN_WARNING "%s detected (calibration quirk enabled)\n",
+	       d->ident);
+	macbook_calibrate_quirk = 1;
+	return 0;
+}
+
+static struct dmi_system_id __initdata calibrate_quirks[] = {
+	{
+	 .callback = init_macbook_calibrate_quirk,
+	 .ident = "Apple MacBook",
+	 .matches = {DMI_MATCH(DMI_PRODUCT_NAME, "MacBook1,1"),},
+	 },
+	{},
+};
+
 static unsigned long preset_lpj;
 static int __init lpj_setup(char *str)
 {
@@ -37,8 +66,16 @@ static unsigned long __devinit calibrate
 	unsigned long tsc_rate_min, tsc_rate_max;
 	unsigned long good_tsc_sum = 0;
 	unsigned long good_tsc_count = 0;
+	unsigned long saved_smi_en = 0;
 	int i;
 
+	if (macbook_calibrate_quirk)
+	{
+		saved_smi_en = inl(0x430);
+		/* mask out bit 3 */
+		outl(saved_smi_en & ~8, 0x430);
+	}
+
 	if (read_current_timer(&pre_start) < 0 )
 		return 0;
 
@@ -94,6 +131,9 @@ static unsigned long __devinit calibrate
 		}
 	}
 
+	if (macbook_calibrate_quirk)
+		outl(saved_smi_en, 0x430);
+
 	if (good_tsc_count)
 		return (good_tsc_sum/good_tsc_count);
 
@@ -117,6 +157,8 @@ void __devinit calibrate_delay(void)
 	unsigned long ticks, loopbit;
 	int lps_precision = LPS_PREC;
 
+	dmi_check_system(calibrate_quirks);
+
 	if (preset_lpj) {
 		loops_per_jiffy = preset_lpj;
 		printk("Calibrating delay loop (skipped)... "