Changed the CPU clock calculation. If no invariant TSC is available, then the max CPU clock is estimated at startup under load, otherwise an average over one second is used.

Hardware/CPU/IntelCPU.cs

@@ -39,6 +39,7 @@ using System;
 using System.Collections.Generic;
 using System.Drawing;
 using System.Diagnostics;
+using System.Globalization;
 using System.Reflection;
 using System.Runtime.InteropServices;
 using System.Threading;
@@ -63,11 +64,14 @@ namespace OpenHardwareMonitor.Hardware.CPU {
     private uint logicalProcessors;
     private uint logicalProcessorsPerCore;
     private uint coreCount;
-    private ulong affinityMask;
+    private bool hasTSC;
+    private bool invariantTSC;    
+    private double estimatedMaxClock;
 
+    private ulong affinityMask;
     private CPULoad cpuLoad;
 
-    private ulong lastCount;    
+    private ulong lastTimeStampCount;    
     private long lastTime;
     private uint maxNehalemMultiplier = 0;    
     
@@ -239,13 +243,33 @@ namespace OpenHardwareMonitor.Hardware.CPU {
           ActivateSensor(totalLoad);
       }
 
-      lastCount = 0;
+      // check if processor has TSC
+      if (cpuidData.GetLength(0) > 1 && (cpuidData[1, 3] & 0x10) != 0)
+        hasTSC = true;
+      else
+        hasTSC = false; 
+
+      // check if processor supports invariant TSC 
+      if (cpuidExtData.GetLength(0) > 7 && (cpuidExtData[7, 3] & 0x100) != 0)
+        invariantTSC = true;
+      else
+        invariantTSC = false;
+
+      // preload the function
+      EstimateMaxClock(0); 
+      EstimateMaxClock(0); 
+
+      // estimate the max clock in MHz      
+      estimatedMaxClock = 1e-6 * EstimateMaxClock(0.01);
+
+      lastTimeStampCount = 0;
       lastTime = 0;
       busClock = new Sensor("Bus Speed", 0, SensorType.Clock, this);      
       coreClocks = new Sensor[coreCount];
       for (int i = 0; i < coreClocks.Length; i++) {
         coreClocks[i] =
           new Sensor(CoreString(i), i + 1, SensorType.Clock, this);
+        if (hasTSC)
           ActivateSensor(coreClocks[i]);
       }
       
@@ -290,6 +314,12 @@ namespace OpenHardwareMonitor.Hardware.CPU {
         Environment.NewLine);
       r.AppendFormat("Affinity Mask: 0x{0}{1}", affinityMask.ToString("X"),
         Environment.NewLine);
+      r.AppendLine("TSC: " + 
+        (hasTSC ? (invariantTSC ? "Invariant" : "Not Invariant") : "None"));
+      r.AppendLine(string.Format(CultureInfo.InvariantCulture, 
+        "Timer Frequency: {0} MHz", Stopwatch.Frequency * 1e-6));
+      r.AppendLine(string.Format(CultureInfo.InvariantCulture,
+        "Max Clock: {0} MHz", Math.Round(estimatedMaxClock * 100) * 0.01));
       r.AppendLine();
 
       for (int i = 0; i < coreCount; i++) {
@@ -306,14 +336,33 @@ namespace OpenHardwareMonitor.Hardware.CPU {
       return r.ToString();
     }
 
+    private double EstimateMaxClock(double timeWindow) {
+      long ticks = (long)(timeWindow * Stopwatch.Frequency);
+      uint lsbBegin, msbBegin, lsbEnd, msbEnd; 
+      
+      Thread.BeginThreadAffinity();
+      long timeBegin = Stopwatch.GetTimestamp() + 2;
+      long timeEnd = timeBegin + ticks;      
+      while (Stopwatch.GetTimestamp() < timeBegin) { }
+      WinRing0.Rdtsc(out lsbBegin, out msbBegin);
+      while (Stopwatch.GetTimestamp() < timeEnd) { }
+      WinRing0.Rdtsc(out lsbEnd, out msbEnd);
+      Thread.EndThreadAffinity();
+
+      ulong countBegin = ((ulong)msbBegin << 32) | lsbBegin;
+      ulong countEnd = ((ulong)msbEnd << 32) | lsbEnd;
+
+      return (((double)(countEnd - countBegin)) * Stopwatch.Frequency) / 
+        (timeEnd - timeBegin);
+    }
+
     public void Update() {
 
       for (int i = 0; i < coreTemperatures.Length; i++) {
         uint eax, edx;
         if (WinRing0.RdmsrTx(
           IA32_THERM_STATUS_MSR, out eax, out edx,
-            (UIntPtr)(1 << (int)(logicalProcessorsPerCore * i)))) 
-        {
+            (UIntPtr)(1 << (int)(logicalProcessorsPerCore * i)))) {
           // if reading is valid
           if ((eax & 0x80000000) != 0) {
             // get the dist from tjMax from bits 22:16
@@ -336,13 +385,19 @@ namespace OpenHardwareMonitor.Hardware.CPU {
           totalLoad.Value = cpuLoad.GetTotalLoad();
       }
 
+      if (hasTSC) {
         uint lsb, msb;
-      bool valid = WinRing0.RdtscTx(out lsb, out msb, (UIntPtr)1);
+        WinRing0.RdtscTx(out lsb, out msb, (UIntPtr)1);
         long time = Stopwatch.GetTimestamp();
-      ulong count = ((ulong)msb << 32) | lsb;
+        ulong timeStampCount = ((ulong)msb << 32) | lsb;
         double delta = ((double)(time - lastTime)) / Stopwatch.Frequency;
-      if (valid && delta > 0.5) {
-        double maxClock = (count - lastCount) / (1e6 * delta);
+        if (delta > 0.5) {
+          double maxClock;
+          if (invariantTSC)
+            maxClock = (timeStampCount - lastTimeStampCount) / (1e6 * delta);
+          else
+            maxClock = estimatedMaxClock;
+
           double busClock = 0;
           uint eax, edx;
           for (int i = 0; i < coreClocks.Length; i++) {
@@ -375,8 +430,9 @@ namespace OpenHardwareMonitor.Hardware.CPU {
             ActivateSensor(this.busClock);
           }
         }
-      lastCount = count;
+        lastTimeStampCount = timeStampCount;
         lastTime = time;
       }
     }
+  }  
 }

Hardware/WinRing0.cs

@@ -97,6 +97,7 @@ namespace OpenHardwareMonitor.Hardware {
       uint regAddress, uint value);
     public delegate bool RdtscTxDelegate(out uint eax, out uint edx,
       UIntPtr threadAffinityMask);
+    public delegate bool RdtscDelegate(out uint eax, out uint edx);
 
     private static InitializeOlsDelegate InitializeOls;
     private static DeinitializeOlsDelegate DeinitializeOls;
@@ -114,6 +115,7 @@ namespace OpenHardwareMonitor.Hardware {
     public static ReadPciConfigDwordExDelegate ReadPciConfigDwordEx;
     public static WritePciConfigDwordExDelegate WritePciConfigDwordEx;
     public static RdtscTxDelegate RdtscTx;
+    public static RdtscDelegate Rdtsc;
 
     private static void GetDelegate<T>(string entryPoint, out T newDelegate) 
       where T : class 
@@ -142,6 +144,7 @@ namespace OpenHardwareMonitor.Hardware {
       GetDelegate("ReadPciConfigDwordEx", out ReadPciConfigDwordEx);
       GetDelegate("WritePciConfigDwordEx", out WritePciConfigDwordEx);
       GetDelegate("RdtscTx", out RdtscTx);
+      GetDelegate("Rdtsc", out Rdtsc);
 
       try {
         if (InitializeOls != null && InitializeOls())

Properties/AssemblyInfo.cs

@@ -69,5 +69,5 @@ using System.Runtime.InteropServices;
 // You can specify all the values or you can default the Build and Revision Numbers 
 // by using the '*' as shown below:
 // [assembly: AssemblyVersion("1.0.*")]
-[assembly: AssemblyVersion("0.1.26.1")]
-[assembly: AssemblyFileVersion("0.1.26.1")]
+[assembly: AssemblyVersion("0.1.27.0")]
+[assembly: AssemblyFileVersion("0.1.27.0")]