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<title> Information for SiS Users
<author> Xavier Ducoin (<it>xavier@rd.lectra.fr</it>)
<date> 27 February 1998

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<sect> Introduction <p>

This driver was primarily written for the SiS86c201.  It also works
on the 202 and the 205 chips.  Support for other SiS products is
not available in XFree86 release 3.3.2.  Drivers for the 5597/8 are
currently under development and should be available in the next release.

The driver supports many advanced features.  These include:
<itemize>
  <item>Linear Addressing
  <item>8/15/16/24 bits per pixel
  <item>Fully programmable clocks are supported
  <item>H/W cursor support
  <item>BitBLT acceleration of many operations
  <item>XAA support (XFree86 Acceleration Architecture)
</itemize>

<sect> Supported chips <p>

<descrip>
<tag>SiS 86c201</tag>
	(External hardware clock)
<tag>SiS 86c202, SiS 86c205</tag>
	(Internal clock synthesizer)
</descrip>

Color expansion is not supported by the engine in 16M-color graphic mode.

<sect> XF86Config Options <p>

The following options are of particular interest for the SiS driver. Each of
them must be specified in the `svga' driver section of the XF86Config file,
within the Screen subsections of the depths to which they are applicable
(you can enable options for all depths by specifying them in the Device
section).

<descrip>
<tag>Option &dquot;noaccel&dquot;</tag>
	By default the XAA (XFree86 Acceleration Architecture) is used.
	This option will disable the use of the XAA and will enable the old
	BitBlt acceleration operations. (see below).
<tag>Option &dquot;hw_clocks&dquot;</tag>
	On chips 86c202 and later, the default is to use the programmable
	clock for all clocks. It is possible to use the fixed clocks
	supported by the chip instead of using this option (manufacturer
	dependent).
<tag>Option &dquot;sw_cursor&dquot, &dquot;hw_cursor&dquot;</tag>
	The default is for using the hardware cursor.
<tag>Option &dquot;no_linear&dquot;</tag>
	By default linear addressing is used on all chips.
	However this might be broken in some implementations. It is
	possible to turn the linear addressing off with this option.
	Note that H/W acceleration and 16/24bpp are only supported with
	linear addressing.
<tag>Option &dquot;no_bitblt&dquot;</tag>
	This option will disable the use of all the BitBLT engine.
	It is useful for problems related to acceleration problems.
	In general this will result in a reduced performance.
<tag>Option &dquot;no_imageblt&dquot;</tag>
	It is useful for problems related to image writing, and possible
	stipple acceleration problems. In general this will result in a reduced
	performance.
</descrip>


<sect> Modelines <p>

When constructing a modeline for use with the Sis
driver you'll need to consider several points:
<itemize>
  <item>H/W Acceleration.  The H/W cursor, and fill operations
	currently allocate memory of the video ram for there own use.
	If this is not available these functions will automatically be
	disabled.
  <item>Dot Clock
</itemize>

<sect> Troubleshooting <p>

With intensive generation there is a snow phenomenon on the screen.
Can't remove it even if I used the fifo low/high water mark dumped
from W95.


With intensive generation in 1024x768 65 Mhz sometimes some points (rubbish,
fuzz... hard to explain) appear in memory, like memory
violations or memory corruption.
It looks like an electronic refresh not well done or VClk too near
the MClk.
I use the default Mclk set by BIOS.
It is hard to reproduce this problem (It can take one hour,
two or more).
I can't reproduce this problem in 1024x768 75 MHz or 1280x1024 110 MHz
or 1152x900 95 MHz.

<verb>
$XFree86: xc/programs/Xserver/hw/xfree86/doc/sgml/SiS.sgml,v 3.3.2.1 1998/02/27 02:45:24 dawes Exp $
</verb>

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