                          Information for SiS Users

                   Juanjo Santamarta (<santamarta@ctv.es>)

                                5 March 2000

1.  Introduction

This driver was primarily written for the SiS6326 and SiS530 by Alan Houri-
hane.  It also works on 5597/5598 chips, and probably on older SiS862X5 fam-
ily.

The driver supports :

   o Linear Addressing

   o 8/15/16/24 bits per pixel

   o Fully programmable clocks are supported

   o H/W acceleration and cursor support

   o XAA support (XFree86 Acceleration Architecture)

2.  XF86Config Options

The following options are of particular interest for the SiS driver. Each of
them must be specified in the Device section of the XF86Config file for this
card.

      Option "SetMclk"
            This option lets you to modify the memory clocking of your card.
            (only for 5597 and 6326) Modifying the memory timings can destroy
            the device, but usually the only ill effects of overclocking is
            to have some noise an drawing errors, but BE CAREFUL. Usually a
            little increment can improve the drawing speed, and allows also
            higher dotclocks.  The server reports default memclock on start-
            ing messages, so take it as a base. Units are in KHZ.

      Option "DacSpeed"
            This option lets you to modify the maximum allowed dotclock).

      Option "sw_cursor", "hw_cursor"
            The default is for using the hardware cursor.

      Option "Turboqueue"
            5597/8 and 6326 have the option to extend the engine command
            queue on VRAM. With extended queue length, the driver only checks
            queue status on some color-expansion commands. This gives some
            performance improvement, but is possible to lose some commands,
            corrupting screen output. As the size of extended command queue
            is 16-32K, the probability is very low, but exists. The perfor-
            mance gain observed is around 8-10%. Currently, using this option
            will occasionally freeze the acceleration engine, causing weird
            image display.

      Option "FastVram"
            Enables 1 cycle memory access. Try it. Increased memory bandwidth
            reduces the possibility of glitches and noise on high resolution
            modes.

      Option "PciRetry"

      Option "NoAccel"
            Disables various hardware accelerations.

      VideoRAM size
            The SiS chips can only directly address 4096K bytes of video RAM.
            Some video cards using these chips are shipped with additional
            video RAM.  The videoRAM must be explicitly limited to 4096 for
            those cards.  Attempting to use the additional RAM leads to a
            variety of scrambled screen artifacts.

3.  Modelines

When constructing a modeline for use with the Sis driver you'll need to con-
sider several points:

   o H/W Acceleration.  The H/W cursor, and fill operations currently allo-
     cate memory of the video ram for there own use.  If this is not avail-
     able these functions will automatically be disabled. Also, Turboqueue
     allocate 32k of Vram.

   o Dot Clock. SiS documents the following video modes to work with 6326.
     The max dot clock allowable for your 6326 based board depends also on
     the memory installed on it. Option FastVram can be needed for high dot
     clocks to work. Of course, the memory installed must allow 1 cycle R/W.

     SiS recommended video modes for 6326:

           640x480 :
                 4, 8, 15, 16, 24 bpp at 85Hz Non-interlaced

           800x600 :
                 4, 8, 15, 16, 24 bpp at 85Hz Non-interlaced

           1024x768 :
                 4, 8, 15, 16, 24 bpp at 85Hz Non-interlaced

           1280x1024 :
                 4, 8, 15, 16, 24 bpp at 75Hz Non-interlaced

           1600x1200 :
                 4, 8  bpp at 65Hz Non-interlaced

4.  Troubleshooting

Some video modes with high dot-clocks don't work at all, resulting on black
screen. Lowering dotclock in that case could solve the problem.

Document based on 3.3 version written by Xavier Ducoin.

     Generated from XFree86: xc/programs/Xserver/hw/xfree86/doc/sgml/SiS.sgml,v 3.7 2000/03/06 22:59:24 dawes Exp $

