Linux on the Mac — state of the union [LWN.net]

Linux on the Mac — state of the union

Posted Dec 12, 2016 12:42 UTC (Mon) by l1k (subscriber, #112260)
In reply to: Linux on the Mac — state of the union by aaahaaap
Parent article: Linux on the Mac — state of the union

almost all of them, except for a custom config of the 2015 base model macbook pro 15", have discrete GPUs

The MacBookPro11,4 is the 2015 version without discrete GPU, the MacBookPro11,5 is the one with discrete GPU.

If I understand it correctly in cases where the integrated GPU controls the display outputs I should be able to fully disable the discrete GPU and not incur it's the power usage penalty.

Correct, but that's the case for both muxed and muxless systems. One thing to keep in mind though is that the external DP/HDMI ports can only be driven by the discrete GPU on 2011+ MacBook Pros.

Is there an easy way to figure out to which GPU the display outputs are connected? Maybe the info can be extracted from xrandr and the Xorg + kernel log?

This is e.g. logged in dmesg: "vgaarb: overriding boot device: PCI:0000:01:00.0" (that's the discrete GPU, the integrated is usually 0000:00:02.0). By default the firmware switches to the discrete GPU on boot, but this can be influenced with an EFI variable using tools like gpu-switch (linked in the article) or gfxCardStatus (on macOS). The MacBookPro5 (2008/09, dual Nvidia) is the exception to that rule, it defaults to the integrated GPU.