Comment 83 for bug 1068404

@Nick: I noticed that Freedesktop's bug 56494 affects a system based on AMD Radeon HD 6550M which uses PowerXpress 3.0/Switchable graphics and not PowerXpress 4.0/Dynamic Switchable graphics. It is likely that the bug is not the same.
To clarify the version of PowerXpress supported by the various supported AMD cards, I'll post this short list based on information on AMD site (names are based on information available on AMD site and on the slides which can be viewed on http://www.slideshare.net/AMD/amd-enduro-technology):

PowerXpress 3.0/Switchable Graphics: HD 6300M series, HD 6500M series.
PowerXpress 4.0/Dynamic Switchable Graphics: (HD 6300M series), HD 6400M series, HD 6600M/6700M series, HD 7300M series, HD 7400M series, HD 7500M/7600M series.
PowerXpress 5.0/Enduro: HD 7700M series, HD 7800M series, HD 7900M series

The HD 6300M series is reported as being based both on PowerXpress 3.0 (http://www.amd.com/us/products/technologies/switchable-graphics/Pages/switchable-graphics.aspx) and PowerXpress 4.0 (http://www.amd.com/us/products/notebook/graphics/amd-radeon-6000m/amd-radeon-6300m/Pages/amd-radeon-6300m.aspx), we need to see the report of an user with a GPU based on HD 6300M series to clarify this (apparently the muxless version of PowerXpress 3.0 is not supported on Linux, so if a HD 6300M series GPU uses the muxless version of PowerXpress 3.0 it should have the same issue reported on bug 56494 of Freedesktop).