image corruption when in multiseat mode and "vga!=normal" kernel parameter

Tiago Vignatti vignatti at
Sun Dec 21 16:46:56 PST 2008

Tomasz Chmielewski escreveu:
> Tomasz Chmielewski schrieb:
>> I have a multiseat system with one AGP card (nvidia GeForce FX 5200; 
>> "primary" card, BIOS displays here) and one PCI card (ATI), running Linux.
>> If I start X in "multiseat mode" (X on both cards, two keyboards+mice), 
>> image is corrupted on nvidia AGP card:
>> The corruption happens with nv, nouveau and binary nvidia driver and a 
>> vga= mode different than normal (i.e. vga=791).
>> The corruption does _not_ happen when I don't use vga= parameter (or use 
>> vga=normal).
>> The corruption does not happen if I start X only on one of the cards.
> I replaced the nvidia AGP card for an ATI card and I can see the same 
> corruption.
> So it doesn't seem to be related to the graphics card or the driver, but 
> some strange issue between the X server and Linux framebuffer?

With the current implementation, Multiseat alone already mess the PCI 
configuration space in some weird ways and for sure that if you try 
other crazy combinations you're lost. Don't try do that. See:


Tiago Vignatti
C3SL - Centro de Computação Científica e Software Livre

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