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       svgalib.chips - Information for Chips and Technologies Users


       Information for Chips and Technologies Users
       David Bateman <>
       23nd May 1997

       0. Introduction
       1. "libvga.config" options
       2. Unsupported Chips and Technologies chipsets
       3. Known bugs


       This  is  the  really  only  my  first  attempt  to get a working fully
       featured driver for the Chips and Technologies  chipset  to  work  with
       svgalib(7).  As such the only machine that I know it will work on is my
       own. If you use this  software  then  at  this  point  I’m  still  very
       interested  in hearing from you by e-mail. Include full details of your
       chipset, amount of videoram and whether you have a VL-Bus  or  PCI  bus

       This  server  was  written  using  the svgalib(7) patch from Sergio and
       Angelo Masci as a starting point. This version of  the  code  resembled
       the  XFree  server code that was used up to XFree 3.1.2. As such it was
       incapable of programming the clocks, using linear addressing, Hi-Color,
       True-Color  modes  or  the hardware acceleration. All of these features
       have since been added to the code. In addition support for  the  65525,
       65535,  65546, 65548, 65550 and 65554 have been included. The 64200 and
       64300 chips are unsupported, however these chips are  very  similar  to
       the 6554x chips which are supported.

       At  this point this code is only confirmed to work correctly on a 65545
       VL-Bus machine. However  as  much  of  the  code  was  stolen  from  my
       experiences  with  writing  code  for XFree I hope not to have too many
       problems with other machines.  However  if  you  run  this  code  on  a
       65545/48  PCI  machine  or  a  65550/54  machine then I am particularly
       interested in hearing of any success or failure stories.

1. "libvga.config" OPTIONS

       The first thing to note is that the option parser for svgalib(7) is not
       very  robust. Hence if you make some typing mistakes, you can have some
       very strange effects. I’ve set out below the  libvga.config(5)  options
       that  are  of  particular  interest  to  Chips  and Technologies users.
       Normally    this    configuration    file    can    be     found     at

       HorizSync MIN MAX
              Often  LCD  panels  has  very  different  specifications for the
              horizontal sync than CRT’s do.  Hence  often  you’ll  need  this
              option,  particularly  if you are using the XFree like modelines
              described below. The two floating point numbers  specified  will
              set the minimum and maximum allowed horizontal sync in kHz.

       VertRefresh MIN MAX
              Similar  to  the  above, but this sets the LCD or CRT’s vertical
              refresh rate in Hz.

       modeline 640x480 20.00 640 688 704 776 480 480 481 486
              This option allows you to specify XFree like modelines to use in
              preference to the in built modelines. Often LCD panels will need
              very different pixel clocks and timings than CRT’s.  Hence  this
              option  allows  you  to  specify  these. Note that the LCD panel
              timings are related to the panel size and  not  the  mode  size.
              Therefore  by default the BIOS setting already uploaded into the
              registers are used by  default.  See  the  "UseModeline"  option
              below if you wish to override these.

       chipset C&T 5 1024
              These  option  allows the user to specify the chipset to use and
              the amount of installed memory in  kBytes.  Currently  supported
              chipsets are

                           0    65520
                           1    65525
                           2    65530
                           3    65535
                           4    65540
                           5    65545
                           6    65546
                           7    65548
                           8    65550
                           9    65554

       TextClockFreq 25.175
              One  major  difference  between  this  code  and  the previously
              available support for the Chips  and  Technologies  chipsets  is
              that  it supports the use of programmable clocks. Because of the
              way that the Chips and Technologies chips program the  VCO  from
              the  registers,  there  is  no  way  to  be  sure to recover the
              previously programmed clock value.   Hence  the  driver  assumes
              that the console clock is 25.175MHz. This will be wrong for many
              machines. However I have supplied this option to use a different
              value that might be more suitable for your machine.

              This  option  disables  the  use of the linear framebuffer. This
              might  be  useful  for  machines   that   have   broken   linear

       linear Allow,  but  don’t enforce the use of the linear framebuffer. As
              this is the default anyway, I don’t see that this option is much

       setuplinear 0xC0000000
              For  VL-Bus  machines  I  expect  that  the  linear  framebuffer
              starting address will be setup correctly.  However  to  get  the
              starting address for PCI machines requires access to the MEMBASE
              register in the PCI address  space.  Code  to  do  this  doesn’t
              currently  exist  with  svgalib(7),  and  so I’ve taken the easy
              option of just testing a few known PCI starting  addresses.  For
              now  these  are  just  0xFE000000,  0xFD000000,  0x41000000  and
              0xC0000000. If you have a different starting  address  then  the
              linear  framebuffer  will  be unusable. You might like to report
              your starting address to me so that I  can  include  it  in  the
              probing  code,  but  till then this option can be used to set up
              the correct address. This option just forces the  given  address
              to  be  the  only  one  probed.  It  doesn’t  force  the  linear
              framebuffer to be used.

       LCDPanelSize 800 600
              For some machines the LCD panel size is incorrectly probed  from
              the  registers.  This  option forces the LCD panel size to be as
              specified. If you have a black band down one side  of  your  LCD
              display  you  might  very well need this option. Also if you are
              using the option "fix_panel_size" in XFree then this option  has
              a  similar  effect.  This option can be used in conjunction with
              the option "UseModeline" to program all the panel timings  using
              the  modeline  values.  Two machines that are known to need this
              option are the HP  Omnibook  5000CTS  and  the  NEC  Versa  4080
              800x600 TFT machines.

              The flat panel timings are related to the panel size and not the
              size  of  the  mode  specified.  For  this  reason  the  default
              behaviour  of the svgalib(7) is to use the panel timings already
              installed in the chip. The user can force the panel  timings  to
              be  recalculated from the modeline with this option. However the
              panel size will still be probed. Two machines that are known  to
              need  this  option  are  the HP Omnibook 5000CTS and the Prostar
              8200. You are advised to check the README.chips that  come  with
              XFree for more details.

              This  option  disables  the use of H/W acceleration. As far as I
              know the only thing that currently uses the H/W acceleration  is
              libvgagl,  so this might not be a problem anyway. However if you
              see corruption of the graphics on the screen try this option and
              see if it goes away.

              For 24bpp on TFT screens, the server assumes that a 24bit bus is
              being used. This can result in a reddish tint to 24bpp mode  for
              machines  that  actually have a 18 bit bus. This option, selects
              an 18 bit TFT bus. Note that using this option with a 24 bit bus
              machine  will  similarly  discolour the screen. For other depths
              this option has no effect.

              The default behaviour of svgalib(7) is to leave  the  stretching
              and  centring  registers  completely  alone.  However  for  some
              machines this might result in poorly placed modes, or modes that
              don’t  fill  the  whole screen. These two options can be used to
              centre and stretch  the  mode  on  the  screen.  Note  that  for
              instance  a  Center  DISABLE might follow a Center ENABLE in the
              config file. Only the last option takes effect.


       The 64200 and 64300 chips are unsupported. However  by  specifying  the
       chipset in your libvga.config as either a

       chipset C&T 3 2048
              Use 65535 for a 64200 assuming 2M of video ram, or

       chipset C&T 7 2048
              Use 65548 for a 64300 assuming 2Mb of video ram

       then  svgalib  can  be  made to give limited support to these chipsets.
       Note that the paged addressing mode of the 65548 chip and  earlier  can
       only  address upto 1Mb of video ram. If the additional memory is needed
       then linear addressing must be used!! Note that support  of  the  64xxx
       chips  has  not  been tested at all, and the above is just a suggestion
       that I believe will work.


       One persistent and annoying bug is that the text mode stretching on LCD
       displays is not always restored correctly for 65550 and 65554 machines.
       This is to do with the manner  in  which  the  extended  registers  are
       restored  and  what  is being done with the synchronous reset while the
       registers are restored. As I don’t have a 65550 or 65554 machine of  my
       own on which to test this code, I have been unable to fix this problem.
       In most circumstances an LCD-CRT switch will restore the LCD stretching
       to the desired state.





       svgalib(7), libvga.config(5).


       of    the    driver   and   this   documentation   is   David   Bateman
       <>.  However, it  was  slightly  reformatted  by
       Michael Weller <>.