*BSD News Article 72093


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From: "Stephen E. Halpin" <seh@quadrizen.com>
Newsgroups: comp.windows.x.i386unix,comp.unix.bsd.freebsd.misc
Subject: ATI GUPro2MB w/68875 at 16bpp - how do I get past the 67.5MHz dot clock limitation?
Date: Thu, 27 Jun 1996 00:12:00 -0400
Organization: Quadrizen
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Greetings.  I have an ATI Graphics Ultra Pro 2MB EISA card with
a 68875 RAMDAC.  I would like to run this card at 1024x768x16@70Hz,
but there is a constant compiled into the server limiting the 16bpp
mode to 67.5MHz.  I noticed that the 8bpp case is limited to 80MHz
unless a 34075 (68875 as well) is present, in which case the limit
in the 8bpp case is raised to 135MHz (I should note that the server
is version 3.1.2 as released on the FreeBSD 2.1 distribution from
Walnut Creek CDROM.)  Im wondering if updating the file:

  /usr/X11R6/src/xc/programs/Xserver/hw/xfree86/accel/mach32/mach32.c

to conditionally upgrade the maximum 16bpp dot clock to 75MHz in the
case of the 34075 as it does for the 8bpp case is a reasonable solution,
or are there other parts of the server that would need to be updated?
(I know that ../../common/Mach32.c would need an additional constant
and variable - Im more concerned about other RAMDAC configuration stuff.)
Even though the 68875 will run at 75MHz, will the 34075 (the server
seems to equate these two chips)?  If so, is this a change that should
be propagated back to the maintainers?  Ive been through the XFree
web site, FAQs, Alta Vista, the Red Hat database, etc... and no one
seems to have addressed this yet.  I dont have chip or board specs to
refer to here either, but Im hoping this sounds familiar to someone...

Thanks for any help or ideas,  -Steve