https://bugzilla.kernel.org/show_bug.cgi?id=109101
Bug ID: 109101 Summary: [A10-7800] CPU is capped to 3GHz if BAPM is enabled Product: Drivers Version: 2.5 Kernel Version: 4.2.6 Hardware: x86-64 OS: Linux Tree: Fedora Status: NEW Severity: normal Priority: P1 Component: Video(DRI - non Intel) Assignee: drivers_video-dri@kernel-bugs.osdl.org Reporter: immarcescibilis@outlook.com Regression: No
I have an A10-7800 APU with a 3.5GHz clock (3.9/3.8/3.6 turbo) on an MSI A88XM-E45 board that doesn't seem to suffer from the lack of BAPM, since it was disabled by default and I had to enable it manually, after doing some research on how to enable TurboCore on Linux. The fact of the matter is not only that it doesn't work at all, but that it caps the CPU clock to 3GHz even on full load. If I disable BAPM, the clocks raise normally to 3.5GHz. In my tests, I've noticed a couple of things:
- Cool'n'Quiet is irrelevant. BAPM throttles the CPU clock whether Cool'n'Quiet is disabled or enabled; - With BAPM enabled, both CPU and GPU temperatures rise together when on full load, even if there's no GPU usage; - The turbo frequencies are never reached.
I made all measurements with turbostat while running either POV-Ray or stress --cpu.