AMD Is Disabling DPM Support For RV770 GPUs
Written by Michael Larabel in AMD on 19 April 2014 at 04:00 PM EDT. 23 Comments
For the many owners of "RV770" hardware out there with the once popular Radeon HD 4850 and HD 4870 graphics cards, AMD open-source developers are now proposing the dynamic power management (re-clocking) support be disabled by default to deal with open bugs.

AMD's Alex Deucher sent out a patch on Friday to disable Dynamic Power Management on the RV770 by default. The DPM for the RV770 was enabled by default with the Linux 3.13 kernel and it yields better/lower power consumption while idling, better performance if the video BIOS sets lower clock speeds at boot time, and with the lower power consumption can also come lower heat output. However, some users have reported issues with RV770 GPUs in using the Linux 3.13 kernel and newer. (In my personal testing of several different RV770 GPUs, I haven't encountered any issues with Linux 3.13+.)


Among the issues reported is the Linux 3.13 kernel and newer hanging the machine now that Radeon DPM is enabled, a fatal machine check when booting Linux 3.13 with an RV770 GPU, and other kernel hanging problems. With this simple patch, RV770 DPM is now disabled by default with the simple message of "There seem to be stability issues on a number of cards."

AMD's Christian K├Ânig has added this patch already to his merge queue for the Linux 3.15 kernel. Hopefully AMD developers will soon be able to sort out the RV770 GPU DPM issues given that this hardware was once very popular with AMD Linux users and is still found out in many systems with the GPUs having launched just six years ago.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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