Phenom II X6 Performance Under Linux Below Expectations
In testing the Phenom II X6, Linux Magazine noticed that AMDs new processor doesn't have the full performance under the current Linux kernel. A bug in Linux power management throws a wrench into the six-core processing.
With Ubuntu 9.04 and kernel 2.6.28, the Phenom II X6 1090T processor exhibited 19% better performance, much like Intel's "Gulftown" Core i7 980, in the LUbench benchmark. However, the performance was far more disappointing with Ubuntu 9.10 under kernel 2.6.31. Only by deactivating AMD's Cool'n'Quiet power-saving technology did the Phenom II X6 get anywhere near the expected performance with Ubuntu 9.10.
AMD's Operating Systems Research Center (OSRC) in Dresden, responsible for Linux development under the direction of Chris Schlaeger, confirmed that the new Turbocore mode of the Phenom II X6 was getting into conflict with the kernel's powernow-k8 frequency regulator module. The module falsely assumes the turbo clock as the maximum frequency. But because only the CPU itself can do the overclocking, this leads to a Turbocore knockout. Even a reduction to miminum clocking is impossible. The problem affects all AMD CPUs with the Turbocore feature under kernel 2.6.30 and later. The only available CPUs with Turbocore right now are the Phenom II X6 1055T and 1090T.
AMD has already sent a relevant patch upstream. The chipmaker is encouraging distro maintainers to update with this patch as soon as possible. The patch should be included in the next Ubuntu 10.04 kernel update. To determine if the issue affects your system, use the following command:
dmesg | grep "pstate 0"
Alternatively, use a widget or applet that shows all available processor clock rates.
If the maximum frequency (pstate 0) is shown as 3600 MHz for the 1090T or 3300 MHz for the 1055T, the system's performance is reduced.
Until the patch is available, Linux users should deactivate Cool'n'Quiet in the BIOS, or blacklist the powernow-k8 kernel module (the latter seems a better solution if Windows is also installed).In our tests, the power use is only 17 watts higher when idling, at least under the unaffected kernel in Ubuntu 9.04. No difference was measured under heavy load, whether it was with one core or all six.
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
![Learn More](https://www.linux-magazine.com/var/linux_magazin/storage/images/media/linux-magazine-eng-us/images/misc/learn-more/834592-1-eng-US/Learn-More_medium.png)
News
-
NVIDIA Released Driver for Upcoming NVIDIA 560 GPU for Linux
Not only has NVIDIA released the driver for its upcoming CPU series, it's the first release that defaults to using open-source GPU kernel modules.
-
OpenMandriva Lx 24.07 Released
If you’re into rolling release Linux distributions, OpenMandriva ROME has a new snapshot with a new kernel.
-
Kernel 6.10 Available for General Usage
Linus Torvalds has released the 6.10 kernel and it includes significant performance increases for Intel Core hybrid systems and more.
-
TUXEDO Computers Releases InfinityBook Pro 14 Gen9 Laptop
Sporting either AMD or Intel CPUs, the TUXEDO InfinityBook Pro 14 is an extremely compact, lightweight, sturdy powerhouse.
-
Google Extends Support for Linux Kernels Used for Android
Because the LTS Linux kernel releases are so important to Android, Google has decided to extend the support period beyond that offered by the kernel development team.
-
Linux Mint 22 Stable Delayed
If you're anxious about getting your hands on the stable release of Linux Mint 22, it looks as if you're going to have to wait a bit longer.
-
Nitrux 3.5.1 Available for Install
The latest version of the immutable, systemd-free distribution includes an updated kernel and NVIDIA driver.
-
Debian 12.6 Released with Plenty of Bug Fixes and Updates
The sixth update to Debian "Bookworm" is all about security mitigations and making adjustments for some "serious problems."
-
Canonical Offers 12-Year LTS for Open Source Docker Images
Canonical is expanding its LTS offering to reach beyond the DEB packages with a new distro-less Docker image.
-
Plasma Desktop 6.1 Released with Several Enhancements
If you're a fan of Plasma Desktop, you should be excited about this new point release.