Radeon UMS Mode

Adam K Kirchhoff akirchhoff135014 at comcast.net
Wed Dec 14 20:43:22 UTC 2011

On 12/14/2011 2:55 PM, Thomas D. Dean wrote:
> I have an ASUS P9X79 motherboard, Intel i7-3930K, Radeon HD 6840, ASUS
> V228 monitor.  FreeBSD 9.0(RC2).
> Xorg -configure wants to use the radeon driver.  I know, FreeBSD does
> not have KMS.  'man radeon' talks about options for KMS and UMS, KMS
> only, and UMS only.
> How may I force UMS mode?

You can't.  HD6xxx and higher GPUs will only work with the radeon driver 
with KMS (1).

> I see references on how to do it with the
> 'other' OS, involving radeon.modeset=0.
> # grep -i modeset `find /usr/src/sys -iname \*radeon\*`
> produces nothing.
> When I use the Vesa driver, the monitor reports some modes like
> "1920x1080"x60.0.
> How may I use this mode with the Vesa driver?
> tomdean

What do you mean by "the monitor reports some modes"?  Where do you see 
those modes reported?  Unless the video card manufacturer programmed the 
mode into the cards BIOS (and few do that with HD modes), it's not 
possible to get the vesa driver to work with that mode.  In fact, I'm 
not even sure the vesa driver driver will handle HD modes even if they 
are programmed in.

(1) There are a very few HD6xxx model GPUs that actually use the 
Evergreen chipset which can use the radeon driver (without any 
acceleration) with UMS.

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