Provided by: libsvga1_1.4.3-27_i386
svgalib.chips - Information for Chips and Technologies Users
TABLE OF CONTENTS
Information for Chips and Technologies Users
David Bateman <email@example.com>
23nd May 1997
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
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
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.
Center ENABLE/DISABLE or Stretch ENABLE/DISABLE
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.
2. UNSUPPORTED CHIPS AND TECHNOLOGIES CHIPSETS
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.
3. KNOWN BUGS
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.
of the driver and this documentation is David Bateman
<firstname.lastname@example.org>. However, it was slightly reformatted by
Michael Weller <email@example.com>.