91 lines
3.1 KiB
Groff
91 lines
3.1 KiB
Groff
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.TH setmclk 1 "2 Aug 1997" "Svgalib (>= 1.2.11)" "Svgalib User Manual"
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.SH NAME
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setmclk \- adjust the memory timing of certain Cirrus cards.
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.SH SYNOPSIS
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.BI setmclk
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.SH DESCRIPTION
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This program sets the
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.B memory clock
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of Cirrus 5424/26/28 cards.
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The first three values could be set by utility programs that
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came with my card (AVGA3), but somewhat higher values seem to work (on my
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card at least). It may be that better and more recent Cirrus cards use a
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higher value as boot-up default. It should depend on DRAM speed, but it
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seems to be more dependant on the card logic.
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I have the impression that many Cirrus 542x cards suffer from horrible
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BIOS version/DRAM timing misconfigurations. Perhaps even some versions of
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MS-Windows drivers change the MCLK register. In any case, the boot-up BIOS
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default (0x1c) may be inappropriately low for the type of DRAM timing most
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cards use.
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Using a higher memory clock gives a very significant performance improvement;
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with high dot clock modes (like 640x480x16M or 1150x900x256) performance can
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be more than twice that of the standard 50 MHz clock. This goes for both
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(VLB) framebuffer access and accelerated features (bitblt). This also helps
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XFree86 server performance, but only if the XFree86 Cirrus driver doesn't
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set the memory clock register (it should work for XFree86 1.3 and 2.0).
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Use at your own risk!
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Note that the
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.B dot clock
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is something entirely different. There does not
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seem to be much correlation between the two (i.e. if a high dot clock gives
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screen problems, using a high memory clock is not likely to fix it, other
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than improving speed).
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The actual
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.B memory clock
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is hard compiled into the program. It defaults to 0x1c. You can change this value
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and some suggestiong come in th source of the utility.
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This utility is part of svgalib and can be found in the
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.I utils/
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subdirectory of the original svgalib distribution. However, it is not installed
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by default, s.t. it is unclear where you can find it if your svgalib was install
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linux distribution.
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In case of any such problem, simply get an svgalib distribution from the net. You
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don't need to install it. Just
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.B make
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in the
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.I utils/
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subdirecty. As of this writing,
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.I svgalib-1.2.12.tar.gz
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is the latest version and can be retrieved by ftp from
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.IR "sunsite.unc.edu" " at " "/pub/Linux/libs/graphics"
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and
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.IR "tsx-11.mit.edu" " at " "/pub/linux/sources/libs"
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which will most probably be mirrored by a site close to you.
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.SH SEE ALSO
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.BR svgalib (7),
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.BR vgagl (7),
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.BR libvga.config (5),
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.BR convfont (1),
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.BR dumpreg (1),
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.BR restorefont (1),
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.BR restorepalette (1),
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.BR restoretextmode (1),
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.BR runx (1),
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.BR savetextmode (1),
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.BR fix132x43 (1),
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.BR textmode (1).
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.SH AUTHOR
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This manual page was edited by Michael Weller <eowmob@exp-math.uni-essen.de>. The
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exact source of the referenced utility as well as of the original documentation is
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unknown.
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It is very likely that both are at least to some extent are due to
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Harm Hanemaayer <H.Hanemaayer@inter.nl.net>.
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Occasionally this might be wrong. I hereby
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asked to be excused by the original author and will happily accept any additions or corrections
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to this first version of the svgalib manual.
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