setmclk man page on aLinux

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setmclk(1)		      Svgalib User Manual		    setmclk(1)

       setmclk - adjust the memory timing of certain Cirrus cards.


       This program sets the memory clock of Cirrus 5424/26/28 cards.

       The  first three values could be set by utility programs that came with
       my card (AVGA3), but somewhat higher values seem to work (on my card at
       least). It may be that better and more recent Cirrus cards use a higher
       value as boot-up default. It should depend on DRAM speed, but it	 seems
       to be more dependant on the card logic.

       I  have the impression that many Cirrus 542x cards suffer from horrible
       BIOS version/DRAM timing misconfigurations. Perhaps even some  versions
       of  MS-Windows drivers change the MCLK register. In any case, the boot-
       up BIOS default (0x1c) may be inappropriately low for the type of  DRAM
       timing most cards use.

       Using  a	 higher	 memory	 clock	gives  a  very significant performance
       improvement;  with  high	 dot  clock   modes   (like   640x480x16M   or
       1150x900x256)  performance  can be more than twice that of the standard
       50 MHz clock. This goes for both (VLB) framebuffer access and  acceler‐
       ated features (bitblt). This also helps XFree86 server performance, but
       only if the XFree86 Cirrus driver doesn't set the memory clock register
       (it should work for XFree86 1.3 and 2.0).  Use at your own risk!

       Note that the dot clock is something entirely different. There does not
       seem to be much correlation between the two (i.e. if a high  dot	 clock
       gives  screen  problems, using a high memory clock is not likely to fix
       it, other than improving speed).

       The actual memory clock is hard compiled into the program. It  defaults
       to  0x1c.  You  can  change  this value and some suggestiong come in th
       source of the utility.

       This utility is part of svgalib and can be found in the	utils/	subdi‐
       rectory	of  the	 original  svgalib  distribution.  However,  it is not
       installed by default, s.t. it is unclear where you can find it if  your
       svgalib was install linux distribution.

       In  case	 of  any such problem, simply get an svgalib distribution from
       the net. You don't need to install it. Just make in the	utils/	subdi‐
       recty.  As of this writing, svgalib-1.2.12.tar.gz is the latest version
       and   can   be	retrieved   by	  ftp	 from    at
       /pub/Linux/libs/graphics	 and at /pub/linux/sources/libs
       which will most probably be mirrored by a site close to you.

       svgalib(7),  vgagl(7),	libvga.config(5),   convfont(1),   dumpreg(1),
       restorefont(1),	  restorepalette(1),	restoretextmode(1),   runx(1),
       savetextmode(1), fix132x43(1), textmode(1).

       This manual page was edited  by	Michael	 Weller	 <eowmob@exp-math.uni->. The exact source of the referenced utility as well as of the
       original documentation is unknown.

       It is very likely that both are at least to some extent are due to Harm
       Hanemaayer <>.

       Occasionally  this  might be wrong. I hereby asked to be excused by the
       original author and will happily accept any additions or corrections to
       this first version of the svgalib manual.

Svgalib (>= 1.2.11)		  2 Aug 1997			    setmclk(1)

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