diff -Naur linux-2.6.18/arch/x86_64/kernel/pmtimer.c linux-2.6.18-pmtmr/arch/x86_64/kernel/pmtimer.c
--- linux-2.6.18/arch/x86_64/kernel/pmtimer.c
+++ linux-2.6.18-pmtmr/arch/x86_64/kernel/pmtimer.c
@@ -35,6 +35,49 @@
 
 #define ACPI_PM_MASK 0xFFFFFF /* limit it to 24 bits */
 
+
+#define PMTMR_TICKS_PER_SEC 3579545
+#define PMTMR_EXPECTED_RATE \
+  ((LATCH * (PMTMR_TICKS_PER_SEC >> 10)) / (CLOCK_TICK_RATE>>10))
+
+int verify_pmtmr_rate(int override)
+{
+       u32 value1, value2;
+       unsigned long delta;
+       unsigned long count = 0;
+
+       outb((inb(0x61) & ~0x02) | 0x01, 0x61);
+       outb(0xb0, 0x43);
+       outb_p(LATCH & 0xff, 0x42);
+       outb_p(LATCH >> 8, 0x42);
+
+       value1 = inl(pmtmr_ioport) & ACPI_PM_MASK;
+
+       do {
+               count++;
+       } while ((inb_p(0x61) & 0x20) == 0);
+
+       value2 = inl(pmtmr_ioport) & ACPI_PM_MASK;
+       delta = (value2 - value1) & ACPI_PM_MASK;
+
+       /* Check that the PMTMR delta is within 5% of what we expect */
+       if (delta < (PMTMR_EXPECTED_RATE * 19) / 20 ||
+           delta > (PMTMR_EXPECTED_RATE * 21) / 20) {
+
+               timer_mult = PMTMR_EXPECTED_RATE * 1000 / delta;
+               if (override) {
+                       printk(KERN_INFO "PIT running at invalid rate, workaround multiplier set to %d.%d\n",  timer_mult / 1000, timer_mult % 1000);
+                       return 0;
+               }
+
+               printk(KERN_INFO "PM-Timer running at invalid rate: %lu%% of normal - aborting.\n", 100UL * delta / PMTMR_EXPECTED_RATE);
+               return -1;
+       }
+
+       timer_mult = 1000;
+       return 0;
+}
+
 static inline u32 cyc2us(u32 cycles)
 {
 	/* The Power Management Timer ticks at 3.579545 ticks per microsecond.
diff -Naur linux-2.6.18/arch/x86_64/kernel/time.c linux-2.6.18-pmtmr/arch/x86_64/kernel/time.c
--- linux-2.6.18/arch/x86_64/kernel/time.c
+++ linux-2.6.18-pmtmr/arch/x86_64/kernel/time.c
@@ -57,6 +57,7 @@
 
 int nohpet __initdata = 0;
 static int notsc __initdata = 0;
+static int pmtmr __initdata = 0;
 
 #define USEC_PER_TICK (USEC_PER_SEC / HZ)
 #define NSEC_PER_TICK (NSEC_PER_SEC / HZ)
@@ -73,6 +74,7 @@
 unsigned long vxtime_hz = PIT_TICK_RATE;
 int report_lost_ticks;				/* command line option */
 unsigned long long monotonic_base;
+u16 timer_mult = 1000;
 
 struct vxtime_data __vxtime __section_vxtime;	/* for vsyscalls */
 
@@ -716,6 +718,10 @@
 
 	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
 
+	/* 
+	 * (PIT_TICK_RATE / (1000 / 50)) is 59659,
+	 *  so we can't use the timer_mult here.
+	 */
 	outb(0xb0, 0x43);
 	outb((PIT_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
 	outb((PIT_TICK_RATE / (1000 / 50)) >> 8, 0x42);
@@ -725,7 +731,11 @@
 
 	spin_unlock_irqrestore(&i8253_lock, flags);
 	
-	return (end - start) / 50;
+	/* 
+	 * It's safer to use timer_mult on the
+	 * computed value.
+	 */
+	return timer_mult * (end - start) / (50 * 1000);
 }
 
 #ifdef	CONFIG_HPET
@@ -855,8 +865,8 @@
 
 	spin_lock_irqsave(&i8253_lock, flags);
 	outb_p(mode, PIT_MODE);
-	outb_p(val & 0xff, PIT_CH0);	/* LSB */
-	outb_p(val >> 8, PIT_CH0);	/* MSB */
+	outb_p((val * timer_mult / 1000) & 0xff, PIT_CH0);	/* LSB */
+	outb_p((val * timer_mult / 1000) >> 8, PIT_CH0);	/* MSB */
 	spin_unlock_irqrestore(&i8253_lock, flags);
 }
 
@@ -918,7 +928,8 @@
 		cpu_khz = hpet_calibrate_tsc();
 		timename = "HPET";
 #ifdef CONFIG_X86_PM_TIMER
-	} else if (pmtmr_ioport && !vxtime.hpet_address) {
+	} else if (pmtmr_ioport && !vxtime.hpet_address &&
+		verify_pmtmr_rate(pmtmr)) {
 		vxtime_hz = PM_TIMER_FREQUENCY;
 		timename = "PM";
 		pit_init();
@@ -1323,3 +1334,11 @@
 }
 
 __setup("notsc", notsc_setup);
+
+static int __init pmtmr_setup(char *s)
+{
+	pmtmr = 1;
+	return 0;
+}
+
+__setup("pmtmr", pmtmr_setup);
diff -Naur linux-2.6.18/include/asm-x86_64/proto.h linux-2.6.18-pmtmr/include/asm-x86_64/proto.h
--- linux-2.6.18/include/asm-x86_64/proto.h
+++ linux-2.6.18-pmtmr/include/asm-x86_64/proto.h
@@ -42,6 +42,8 @@
 extern void pmtimer_resume(void);
 extern void pmtimer_wait(unsigned);
 extern unsigned int do_gettimeoffset_pm(void);
+extern int verify_pmtmr_rate(int);
+extern u16 timer_mult;
 #ifdef CONFIG_X86_PM_TIMER
 extern u32 pmtmr_ioport;
 #else