AmdMsrTweaker is a command line tool for Windows which allows to reprogram the P-States used by various CPUs and APUs of AMD for their Cool&Quiet power saving technology. The P-States are available via model specific registers and can be changed to allow for undervolting or even overclocking on unlocked chips. This gives greater flexibility compared to a fixed offset voltage in BIOS.

One thing I found particularly interesting is the fact that AMD actually has a competitive advantage here they never really highlighted. To the contrary, on Intel’s chips the registers to control this behavior are write-protected and thus can’t be altered by the user.

The following CPU lines are supported:

- K10 / K10.5 CPUs (various Phenom models): CPU P-States, NB P-States on supported models

- Llano (Family 12h): CPU P-States

- Ontario / Zacate (Family 14h): CPU P-States

- Bulldozer, Piledriver, Trinity, Richland, Kaveri (Family 15h): CPU P-States, NB P-States

Originally, the tool was developed and released by Martin Kinkelin back in 2011 in various forums. He appears to have abandoned development of the tool but I gladly took over. Luckily it was released under an open source license which allowed this to happen in the first place.

Compared to the original version, now known as "v1.0" the following changes have been implemented in "v1.1":

- support for Trinity and Richland APUs

- preliminary support for Kaveri APUs

Without further ado, here you can download the tool:

Here –> AmdMsrTweaker v1.1

To comply with the license and to make sure the tool is available in the future, the source code will be released via GitHub as well. I am currently in the process of cleaning it up a bit for public release.

I have limited time to work on new features, but there are already some features planned to be incorporated in future releases. I am also open to feature suggestions but there are some caveats. For now I don’t plan to develop a GUI. Also I am restricting myself to register programming, I’m not going to mess with PLLs and the like.

Feedback is appreciated. You can drop a comment here, in the respective thread in the XtremeSystems forums or via Twitter @marcuspollice.

Note to the original author:
I have tried to contact you via forums where you promoted the original release of the tool since I didn’t find an e-mail address of yours. Until today I didn’t receive a reply. If you want to comment on the situation, please drop me a line.