http://cpu.rightmark.org/products/rmclock.shtml

RightMark CPU Clock Utility (RMClock) is a small GUI application designed for real-time CPU frequency, throttling and load level monitoring and on-the-fly adjustment of the CPU performance level on supported CPU models via processor's power management model-specific registers (MSRs). In automatic management mode it continuously monitors the CPU usage level and dynamically adjusts the CPU frequency, throttle and/or voltage level as needed, realizing the "Performance on Demand" concept.
Pricing and availability

Basic RMClock version is available free of charge for personal nonS E N S O Rmercial use and for non-profit organizations. No registration or activation is required. For information concerning licensing schemes for commercial use (for-profit organizations), please contact us.
Features

Real-time CPU clock and CPU/OS load level determination and monitoring (with optional logging).
Detection of virtually any form of CPU clock throttling.
Dynamic on-demand CPU performance state (P-state) transitions via real-time adjustment of CPU multiplier (FID) and/or requested voltage level (VID).
Dynamic on-demand CPU clock modulation via real-time transitions between CPU clock throttling levels.
Fine-tuning of advanced CPU-specific power management settings for AMD K7, AMD K8, Intel Pentium M/Centrino platform, Intel Pentium 4 and Xeon, Intel Core Solo/Core Duo/Centrino Duo platform, Intel Core 2, VIA C7 and Transmeta Crusoe/Efficeon CPU families.
Complete support for multi-processor (SMP/HT/multicore) systems.
Windows power management settings and LCD display brightness control (where supported).
Battery information display (general and per-battery) including real-time status display of the battery life time, charge level, charge/discharge rate etc.
CPU core temperature display (available on AMD K8, Intel Core and Intel Core 2 CPU families).

Supported platforms: CPU

Current release of RMClock utility implements the CPU frequency, CPU load and throttling level determination on the following processor models:

AMD K7 (Athlon/XP/MP, Duron, Sempron) and K8 (Athlon 64/FX/X2, Opteron, Dual-Core Opteron, Sempron, Turion 64/X2) family processors.
Intel Pentium II/Celeron, Pentium III/Celeron, Pentium M/Celeron M, Pentium 4/Celeron (Northwood and Prescott cores), Pentium 4 Extreme Edition (Gallatin and Prescott cores), Xeon (Prestonia, Nocona, Cranford, Irwindale, Potomac, Paxville and Dempsey cores), Pentium D and Pentium Extreme Edition (Smithfield, Presler and Cedar Mill cores), Core Solo/Celeron M/Core Duo (Yonah core) and Core 2 Duo/Core 2 Quad/Core 2 Extreme/Xeon (Conroe/Allendale, Merom, Woodcrest, Kentsfield/Clovertown cores).

Dynamic P-state transitions are supported on:

AMD Athlon 64/FX/X2, Sempron, Turion 64/X2, mobile Athlon 64, Opteron and Dual-Core Opteron featuring AMD Cool`n'Quiet(tm) technology.
Mobile or Low-Power Desktop AMD Athlon XP featuring AMD PowerNow!(tm) technology.
Intel Pentium M, Intel Core Solo and Core Duo, Intel Core 2 Duo, Core 2 Quad and Core 2 Extreme, Intel Xeon (Woodcrest and Clovertown cores) featuring Enhanced Intel(R) SpeedStep(tm) technology (EIST).
Intel Pentium 4 600 series (Prescott N0 core), Intel Xeon (Nocona, Cranford, Irwindale, Potomac, Paxville and Dempsey cores), Intel Pentium D 800/900 series (Presler core), Intel Pentium Extreme Edition (Smithfield, Presler and Cedar Mill cores) featuring Enhanced Intel(R) SpeedStep(tm) technology (also known as Demand-Based Switching).

NOTE: Intel(R) SpeedStep(tm) technology and the "old" vision of Enhanced Intel(R) SpeedStep(tm) technology found in mobile Pentium III-M and mobile Pentium 4 processors are not supported.

Dynamic on-demand clock modulation adjustment is supported on:

Intel Pentium M/Celeron M, Intel Pentium 4/Pentium 4 Extreme Edition/Celeron, Intel Xeon, Intel Pentium D/Pentium Extreme Edition, Intel Core Solo/Core Duo, Intel Core 2 Duo/Quad/Extreme featuring On-Demand Clock Modulation (ODCM).

RMClock utility will run on unsupported CPU models, however, in this case, most of its functionality will not be available.
Supported platforms: OS

32-bit Windows NT class OS version 5.0 and higher: Windows 2000, XP, 2003 Server and Vista platforms. No support for Win9x OS family is ever planned.
Support for Windows XP x64 platforms is available since version 1.7 (x64 driver included into the package).
NOTE: Support for 64-bit Windows Vista is currently limited due to the kernel mode driver digital signature requirement of that OS (workarounds are necessary).
NOTE: You must have Administrative rights to install and run this utility.