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machinegod420

Member

Registered: 2015-01-05

Posts: 28

Strange issue with PRIME on ATI/Intel muxless hybrid

Hi guys,
I have a hybrid graphics laptop with arch running on it. As I can tell, there are two choices : catalyst drivers, or the open source drivers. The catalyst drivers apparently don't seem to like working with an xorg server version greater than 1.15, so I don't think many people run that. However, it seems that with DRI_PRIME to switch between cards, I'm getting the exact same performance as with the intel card. Is there a specific way to setup the open source ATI drivers? Or is PRIME the correct way and I'm just doing something wrong.

Xabre

Member

From: Serbia

Registered: 2009-03-19

Posts: 752

Re: Strange issue with PRIME on ATI/Intel muxless hybrid

What's your criteria for performance? What tools have you used to measure it?

machinegod420

Member

Registered: 2015-01-05

Posts: 28

Re: Strange issue with PRIME on ATI/Intel muxless hybrid

I mostly benchmark with video games, Chivalry and a quake3 clone. Basically run both with DRI_PRIME enabled, and disabled, and I get pretty much the exact same fps with both settings. When I run glxinfo though, it displays the correct card

Xabre

Member

From: Serbia

Registered: 2009-03-19

Posts: 752

Re: Strange issue with PRIME on ATI/Intel muxless hybrid

vsync disabled? If you're getting exactly the same numbers, it must be vsync.

vblank_mode=0 glxgears
vblank_mode=0 DRI_PRIME=1 glxgears

Ofcourse, glxgears is not a proper test, even glxspheres, but glxspheres should show a more noticeable difference.

Also, bare in mind that some game launchers are written in such way that they completely ignore DRI_PRIME setting. For example, launcher from GOG games has to be tweaked pretty much for it to start using PRIME.

machinegod420

Member

Registered: 2015-01-05

Posts: 28

Re: Strange issue with PRIME on ATI/Intel muxless hybrid

I'm pretty sure that DRI_PRIME actually turns off vsync and thats pretty much it. When I run glxgears with the PRIME setting, I get much higher fps. But VSync shouldn't be capping my fps at 15.

That may be the case, but I don't know if steam games or Xonotic do that do they? Xonotic seems like a fairly simple game.

Xabre

Member

From: Serbia

Registered: 2009-03-19

Posts: 752

Re: Strange issue with PRIME on ATI/Intel muxless hybrid

If I'm not terribly wrong, DRI_PRIME does disable vsync, but only for DGP, not IGP. And it's the IGP that is responsible for displaying picture on the screen.
(I am no expert, though, I could be speaking nonsense)

But, 15 fps is by far too low. I have Haswell Ci3 with Intel HD4600 + discrete Radeon HD8750M on my laptop. At reasonable settings, given the hardware, it's about 60FPS with DRI_PRIME enabled.

machinegod420

Member

Registered: 2015-01-05

Posts: 28

Re: Strange issue with PRIME on ATI/Intel muxless hybrid

It really is, especially for an old game... I got performance improvements with the catalyst drivers, but I can't get those working with xorg 1.16, and really don't want to roll back past that.