diff --unified --recursive --new-file linux-2.6.5/arch/i386/kernel/cpu/cpufreq/speedstep-ich.c linux-2.6.5.speedstep/arch/i386/kernel/cpu/cpufreq/speedstep-ich.c
--- linux-2.6.5/arch/i386/kernel/cpu/cpufreq/speedstep-ich.c	2004-06-07 20:49:36.000000000 +0000
+++ linux-2.6.5.speedstep/arch/i386/kernel/cpu/cpufreq/speedstep-ich.c	2004-06-08 23:34:00.871702720 +0000
@@ -70,23 +70,52 @@
  *
  *   Tries to change the SpeedStep state. 
  */
-static void speedstep_set_state (unsigned int state, unsigned int notify)
+static void speedstep_set_state (unsigned int cpu, unsigned int state, unsigned int notify)
 {
 	u32			pmbase;
 	u8			pm2_blk;
 	u8			value;
 	unsigned long		flags;
 	struct cpufreq_freqs	freqs;
+	cpumask_t               cpus_allowed, affected_cpu_map;
+	int                     hyperthreading = 0;
+	int                     sibling = 0;
 
 	if (!speedstep_chipset_dev || (state > 0x1))
 		return;
 
+	/* switch to physical CPU where state is to be changed*/
+	cpus_allowed = current->cpus_allowed;
+
+	/* only run on CPU to be set, or on its sibling */
+       affected_cpu_map = cpumask_of_cpu(cpu);
+#ifdef CONFIG_X86_HT
+	hyperthreading = ((cpu_has_ht) && (smp_num_siblings == 2));
+	if (hyperthreading) {
+		sibling = cpu_sibling_map[cpu];
+                cpu_set(sibling, affected_cpu_map);
+	}
+#endif
+	set_cpus_allowed(current, affected_cpu_map);
+        BUG_ON(!cpu_isset(smp_processor_id(), affected_cpu_map));
+
 	freqs.old = speedstep_get_processor_frequency(speedstep_processor);
 	freqs.new = speedstep_freqs[state].frequency;
-	freqs.cpu = 0; /* speedstep.c is UP only driver */
-	
-	if (notify)
+	freqs.cpu = cpu;
+
+	/* no transition necessary */
+	if (freqs.old == freqs.new) {
+	        set_cpus_allowed(current, cpus_allowed);
+		return;
+	}
+
+	if (notify) {
 		cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+		if (hyperthreading) {
+		        freqs.cpu = sibling;
+			cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+		}
+	}
 
 	/* get PMBASE */
 	pci_read_config_dword(speedstep_chipset_dev, 0x40, &pmbase);
@@ -142,9 +171,18 @@
 		printk (KERN_ERR "cpufreq: change failed - I/O error\n");
 	}
 
-	if (notify)
-		cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+	/* allow to be run on all CPUs */
+	set_cpus_allowed(current, cpus_allowed);
 
+	if (notify) {
+	        /* notifiers */
+	        cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+	        if (hyperthreading) {
+		        freqs.cpu = cpu;
+			cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+		}
+		dprintk(KERN_DEBUG "cpufreq: transition on cpu %i from %i kHz to %ikHz completed\n",cpu ,freqs.old ,freqs.new);
+	}
 	return;
 }
 
@@ -253,7 +291,7 @@
 	if (cpufreq_frequency_table_target(policy, &speedstep_freqs[0], target_freq, relation, &newstate))
 		return -EINVAL;
 
-	speedstep_set_state(newstate, 1);
+	speedstep_set_state(policy->cpu, newstate, 1);
 
 	return 0;
 }
@@ -277,12 +315,8 @@
 	int		result = 0;
 	unsigned int	speed;
 
-	/* capability check */
-	if (policy->cpu != 0)
-		return -ENODEV;
-
 	/* detect low and high frequency */
-	result = speedstep_get_freqs(speedstep_processor,
+	result = speedstep_get_freqs(policy->cpu,speedstep_processor,
 				     &speedstep_freqs[SPEEDSTEP_LOW].frequency,
 				     &speedstep_freqs[SPEEDSTEP_HIGH].frequency,
 				     &speedstep_set_state);
diff --unified --recursive --new-file linux-2.6.5/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c linux-2.6.5.speedstep/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c
--- linux-2.6.5/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c	2004-06-07 20:49:36.000000000 +0000
+++ linux-2.6.5.speedstep/arch/i386/kernel/cpu/cpufreq/speedstep-lib.c	2004-06-08 23:34:50.120215808 +0000
@@ -310,20 +310,40 @@
  *                     DETECT SPEEDSTEP SPEEDS                       *
  *********************************************************************/
 
-unsigned int speedstep_get_freqs(unsigned int processor,
+unsigned int speedstep_get_freqs(unsigned int cpu,
+				  unsigned int processor,
 				  unsigned int *low_speed,
 				  unsigned int *high_speed,
-				  void (*set_state) (unsigned int state,
+				  void (*set_state) (unsigned int cpu,
+						     unsigned int state,
 						     unsigned int notify)
 				 )
 {
 	unsigned int prev_speed;
 	unsigned int ret = 0;
 	unsigned long flags;
+	cpumask_t cpus_allowed, affected_cpu_map;
+	int hyperthreading = 0;
+	int sibling = 0;
 
 	if ((!processor) || (!low_speed) || (!high_speed) || (!set_state))
 		return -EINVAL;
 
+	/* switch to physical CPU where state is to be changed*/
+	cpus_allowed = current->cpus_allowed;
+
+	/* only run on CPU to be set, or on its sibling */
+       affected_cpu_map = cpumask_of_cpu(cpu);
+#ifdef CONFIG_X86_HT
+	hyperthreading = ((cpu_has_ht) && (smp_num_siblings == 2));
+	if (hyperthreading) {
+		sibling = cpu_sibling_map[cpu];
+                cpu_set(sibling, affected_cpu_map);
+	}
+#endif
+	set_cpus_allowed(current, affected_cpu_map);
+        BUG_ON(!cpu_isset(smp_processor_id(), affected_cpu_map));
+
 	/* get current speed */
 	prev_speed = speedstep_get_processor_frequency(processor);
 	if (!prev_speed)
@@ -332,7 +352,7 @@
 	local_irq_save(flags);
 
 	/* switch to low state */
-	set_state(SPEEDSTEP_LOW, 0);
+	set_state(cpu, SPEEDSTEP_LOW, 0);
 	*low_speed = speedstep_get_processor_frequency(processor);
 	if (!*low_speed) {
 		ret = -EIO;
@@ -340,7 +360,7 @@
 	}
 
 	/* switch to high state */
-	set_state(SPEEDSTEP_HIGH, 0);
+	set_state(cpu, SPEEDSTEP_HIGH, 0);
 	*high_speed = speedstep_get_processor_frequency(processor);
 	if (!*high_speed) {
 		ret = -EIO;
@@ -354,10 +374,11 @@
 
 	/* switch to previous state, if necessary */
 	if (*high_speed != prev_speed)
-		set_state(SPEEDSTEP_LOW, 0);
+		set_state(cpu, SPEEDSTEP_LOW, 0);
 
  out:
 	local_irq_restore(flags);
+	set_cpus_allowed(current, cpus_allowed);
 	return (ret);
 }
 EXPORT_SYMBOL_GPL(speedstep_get_freqs);
diff --unified --recursive --new-file linux-2.6.5/arch/i386/kernel/cpu/cpufreq/speedstep-lib.h linux-2.6.5.speedstep/arch/i386/kernel/cpu/cpufreq/speedstep-lib.h
--- linux-2.6.5/arch/i386/kernel/cpu/cpufreq/speedstep-lib.h	2004-06-07 20:49:36.000000000 +0000
+++ linux-2.6.5.speedstep/arch/i386/kernel/cpu/cpufreq/speedstep-lib.h	2004-06-08 23:34:06.104907152 +0000
@@ -41,7 +41,7 @@
  * SPEEDSTEP_LOW; the second argument is zero so that no 
  * cpufreq_notify_transition calls are initiated.
  */
-extern unsigned int speedstep_get_freqs(unsigned int processor,
+extern unsigned int speedstep_get_freqs(unsigned int cpu, unsigned int processor,
 	  unsigned int *low_speed,
 	  unsigned int *high_speed,
-	  void (*set_state) (unsigned int state, unsigned int notify));
+	  void (*set_state) (unsigned int cpu, unsigned int state, unsigned int notify));