CrystalCPUID: User Configurable Cool 'n' Quiet

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April 11, 2005 by Jan Kivar

New contributor Jan Kivar is no stranger to SPCR forums visitors. Aside from his interest in quiet computing, Jan has 10 years experience with computers and is studying for a MSc. (Tech.) in his native Finland.

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One of the greatest features of AMD's Athlon 64 processor is Cool 'n' Quiet. This feature supports automatic on-the-fly switching of the processor's multiplier and core voltage based on actual CPU usage. Each model has its own, predefined states, and the switching between these states is controlled by a special driver for Athlon 64 processors released by AMD. Depending on the model, there are 2-5 different states.

In this article, Cool 'n' Quiet refers to the combination of:

  • enabling CnQ in the BIOS,
  • installing the AMD Processor Driver, and
  • enabling the minimal power management feature in Windows 2000/XP.

For more information about Athlon 64 processors, I suggest you read the SPCR article, Athlon 64 for Quiet Power. CnQ is fairly well documented at SPCR and by hardware web sites at large. But in case it is new to you, here is a quick summary:

CnQ allows the processor and the PC as a whole to remain in a cool, low power state except when needed. When the computing load is higher, CnQ brings the processor back to normal voltage and clock speed seamlessly, allowing the PC's full power to be harnessed. When the load drops back down, then the CPU clock speed and voltage are dropped down again. The end result is that in idle, the system runs cooler and draws less power. It can also run with less cooling airflow, which means fans can be slowed down, allowing for reduced noise. Because a large proportion of computers actually remain at idle or low load states more than 90% of the time, the average power, heat and noise reductions can be quite dramatic.

Cool 'n' Quiet is not without flaws. Since the core voltage is changed between predefined values based on CPU load, undervolting is not possible when using CnQ. The processor driver automatically switches to the default voltage whenever CPU load is high, thus nullifying the effect of undervolting. Similar issue exists to some extent with underclocking, and overclocking with CnQ fully enabled is very problematic.

Editor's Note: Undervolting can be used to reduce the heat generated by a processor without any speed penalty. These articles cover the topic fully —


In the fall of 2004 I assembled an AMD A64 3000+ system with an MSI nForce3 250 motherboard and began using a utility called ClockGen that could change the multiplier and core voltage directly within Windows. ClockGen supported all nForce3-based motherboards (also nForce2), but only a few VIA-based motherboards (and also some motherboards for Intel-based systems).

The problem with ClockGen was that it didn't support automatic state switching. So I ended up with two shortcuts in the Quick Launch - one for the default maximum settings, and one for the custom underclocked and undervolted settings. Despite the lack of automatic state switching, it was actually better than CnQ, since I was in charge. If I wanted to keep the processor in the low, custom setting while doing something processor-intensive, I was able to do so, maintaining low power usage and lower fan speeds.

Soon, I got bored with playing with the state switching. Basically I ended up using the custom setting all the time, except when I played games. This was fine since I have little time to play in general. Then one day while browsing the Web I stumbled upon a thread in the AMD forums where somebody had posted a guide how to use PowerNow on Desktop PCs. PowerNow is power-saving technology developed by AMD for mobile computing. Being curious, I checked the CrystalCPUID homepage. After playing with it a bit I started a thread in the forums, which resulted eventually in Mike Chin, the Editor of SPCR, asking me to write this article.


CrystalCPUID is a Windows XP/2000 compatible utility created by a Japanese programmer whose handle is hiyohiyo. It looks and works much like WCPUID or CPU-Z, which are utilities to get information about processor speed, cache, etc. They can also identify different CPU core revisions/steppings. CrystalCPUID is also capable of doing exactly what I previously used ClockGen for: Changing the multiplier and core voltage on-the-fly within Windows. But what is most interesting, CrystalCPUID has a feature called "Multiplier Management", which allows automatic clock speed and voltage management like Cool 'n' Quiet, except that it is user customizable. The rest of this article explains how to use use CrystalCPUID in place of CnQ.

WARNING: This guide is recommended only for experienced users. Following these instructions may render your system unusable. Since each CPU has different undervolting capabilities, using settings identical to the ones described in this guide may cause instability, or make the system unbootable. If you don't know how to reset your motherboard CMOS back to its defaults, you shouldn't be messing with this stuff. Neither the author nor can be held responsible for possible data loss or other damage.

Please note that the entire article refers specifically to CrystalCPUID version The creator of the CrystalCPUID makes frequent updates. We suggest that you study carefully the differences between the latest version and the one referred to here before using it.

Although CrystalCPUID was originally created for use with Athlon 64s, from version 4.3 onward, the software was modified for Enhanced Intel Speedstep Technology (EIST) and on-demand clock modulation (ODCM), Intel's dynamic CPU clock / voltage management features built into the Intel 600 series, the 570J and the Pentium M processors. It also works with the AMD K6 and K7. This article covers operation with the Athlon 64 only.

This guide is for AMD Athlon 64s, both desktop and mobile. Basically that also means Athlon 64 FX and Socket 754 Semprons. Socket 462 (Socket-A) mobile processors are also supported; with care, this guide can also be used with them. It is to be noted that, as with 8rdavcore, only a few S462 motherboards support changing the multiplier and voltage. Neither socket 940 A64 FX nor Opteron processors are supported.

All motherboards based on the nVidia nForce3/4 chipset are supported. Support for VIA chipset motherboards is uncertain at time of writing. Some might work, some might not.


In addition to CrystalCPUID, you need Prime95 for stability testing. CPU-Z is also needed, as it currently offers more information about the CPU than CrystalCPUID, such as core voltage and core revision in clear text.

Here are the installation procedures:

1. Check if "Cool 'n' Quiet" option is found in BIOS, and turn it on. In some cases, there is no such option. This does not automatically mean that the board doesn't support Cool 'n' Quiet, just that the user cannot change the setting. In this case, it might be turned off permanently by the motherboard maker. A BIOS upgrade could enable it, though, so check the manufacturer's site for BIOS updates, or search the forums. Some Socket 754 motherboards were problematic and had Cool 'n' Quiet disabled, but all Socket 939 motherboards should support Cool 'n' Quiet out-of-the-box or after enabling a switch in the BIOS.

2. Configure Windows NOT to use Cool 'n' Quiet. Go to Control Panel -> Power Options, and ensure that "Minimal Power Management" is not selected. Note that this doesn't have any effect if the AMD processor driver (CnQ software) is not installed. Whether the AMD processor driver is installed or not is irrelevant for CrystalCPUID.

3. Install and setup Prime95. Start Prime95, and press "Just stress testing". Then click Advanced and select Password. It's given in the readme, but to save time, try "9876" without the quotation marks. After the password is set, click Advanced and select Priority. Set it to 9.

4. CPU-Z doesn't have an installer, so just make a directory, unzip the archive there and run.

5. CrystalCPUID has no installer either. I strongly recommend making a directory "CrystalCPUID" in "C:\Program Files\". Since a shortcut is not automatically created, I suggest that you make one to the desktop. It will be only temporary, and in the end of the guide it will be moved to the Startup-directory. Windows drag and drop behaves irrationally when dragging within a drive; be sure to drag the executable's icon using the right mouse button and then selecting "Create Shortcuts Here".

6. Disable any screen savers. This makes it easier to check on Prime95's status.

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