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Re: MGA400

On Tue, 21 Aug 2001, Michael Schwendt wrote:

>>>   (EE) MGA(0): Given depth (32) is not supported by this driver
>>> It runs at 24 bpp, but some applications (like kwintv or zapping)
>>> don't like this and draw over the whole screen horizontally,
>>> probably assuming 32 bit pixel width.
>>> Can I do anything to fix this?
>>Man XFree86 .... look at the -depth and -fbbpp options. You seem to
>>want -depth 24 (24 bits used for colors) and -fbbpp 32 (32 bits per
>With 3.3.6 I use this line in /etc/X11/xdm/Xservers:
>:0 local /usr/X11R6/bin/X -bpp 32
>With 4.0.3-5, the driver doesn't support 32 bpp. Hence I've have
>taken it out and have the following in XF86Config-4:

XFree86 4 supports the same modes as 3.3.6 did, only it does so 
in a more sensible way.  "depth" refers to the number of bits of 
active color information.  This value is one of 1/2/4/8/15/16/24
There is no such thing as 32 bit color.  The bit width of a pixel 
on the other hand, is now refered to as "fbbpp", and is 
8/16/24/32 depending on the mode and visual.

So depth 8 is fbbpp 8, depth 15 is fbbpp 16, depth 16 is fbbpp 
16, depth 24 is either fbbpp 24 or 32 depending on the driver 
implementation and hardware capabilities.  In general depth 24 
uses fbbpp 32.

>Section "Screen"
>    Identifier "Screen0"
>    Device "Matrox Millennium G400"
>    Monitor "S/M 950p+"
>    DefaultDepth 24
>    Subsection "Display"
>        Depth 24
>        Modes "1024x768" "800x600"
>#        Modes "1280x1024" "1152x864"
>    EndSubSection
>Apparently, this enables the 24 bpp mode by default, which breaks
>kwintv on Seawolf.

My guess is a buggy kwintv.

>>(Usually, though, it's best to just trust the Xserver on what fbbpp it
>>picks for a given depth, and complain to the authors of broken
>Aha, so kwintv is broken with 24 bpp true colour?


>Why doesn't the driver support 32 bpp anylonger? Just found this
>in the log:

It does AFAIR.

>(==) MGA(0): Default visual is TrueColor
>(II) MGA(0): [drm] bpp: 24 depth: 24
>(II) MGA(0): [drm] Direct rendering only supported in 16 and 32 bpp modes

Defaultdepth 24
Defaultfbbpp 32

>(II) MGA(0): Using 4693 lines for offscreen memory.
>(**) MGA(0): DPMS enabled
>(II) MGA(0): Using overlay video
>(II) MGA(0): direct rendering disabled

Mike A. Harris                  Shipping/mailing address:
OS Systems Engineer             190 Pittsburgh Ave., Sault Ste. Marie,
XFree86 maintainer              Ontario, Canada, P6C 5B3
Red Hat Inc.                    Phone: (705)949-2136
http://www.redhat.com           ftp://people.redhat.com/mharris

Red Hat XFree86 mailing list:   xfree86-list redhat com
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