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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 im-
       provement; 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	 accelerated  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 in-
       stalled 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),  re-
       storefont(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-es->.	 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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