Re: 16bpp and above on Linux/XFree86 on 701C

["John H. Kim" <jokim@mit.edu>]

Elvin wrote:

>        Just a simple question. Can Xfree86 go up to 16bpp and above on 
> the 701C ? WIndows works fine with >8bit (Thought 24 bpp, not much diff.)
>        And one big question, how do I set XFree86 to go 16bpp and 32bpp ???

Here's my answer a month ago:
---------- Forwarded message ----------
Date: Thu, 6 Jun 1996 11:10:48 -0400 (EDT)
From: "John H. Kim" <jokim@MIT.EDU>
To: Bjoern Stabell <bjoerns@stabell.priv.no>
Cc: thinkpad@cs.utk.edu
Subject: Re: display and graphics chip set of 701s

On Thu, 6 Jun 1996, Bjoern Stabell wrote:

> Does anyone know how many bits of each RGB component the display and
> graphics chip set can handle [on the TP701]?

The 701 uses the C&T 65545 video chipset.  It isn't originally designed
for 24-bit color, but IBM tweaked something to get 24-bit color to work
under DOS-VESA, Windows, and OS/2.  It seems to work except it requires
a strange synch frequencies many monitors can't handle.  On the LCD I
get a wavy white line along the right side.  Not that 24-bit color is
useful on an LCD - I tested it and it's indistinguishable from 16-bit
color on my TFT, other than being slower and the white line.  The 16-bit
(64k and 32k color) modes are standard, and fully supported under DOS,
Windows, and OS/2.

> I'm using Linux, and the SVGA X server I use doesn't seem to understand
> anything beyond 640x480 in 256 colors with a resolution of 6 bits in each
> of the three color dimensions (RGB).  Anyone know of a better server or if
> better support is planned for the ct65545 chipset?

There XFree server offers minimal support for the CT65545.  It'll only
do 8-bit video (256 colors, or 8 bits from a palette of 18-bits, which
is where Bjoern gets the "6 bits in each..." figure).  It doesn't even
use the video acceleration or programmable clock.

You can buy the AcceleratedX server for $99.  It is also limited to 8-bit
color, but it does use the acceleration and programmable clock.
http://www.xinside.com

There's also been some pre-release work to enable the XFree server to
use acceleration and 16-bit and 24-bit color.  I've tried several of
these "alpha" drivers without success.  They put the video in an unusable
mode.  5% of the time it is unrecoverable, requiring I reboot.  The other
95% of the time, I can get it back to a usable mode by hitting Fn+F1.
I suspect there's something simple I'm missing here, but I don't have the
time or knowledge to look into it further.
http://www.cygnus.com/~raeburn/ct5xx.html
http://www.castle.net/X-notebook/index_linux.html

> Tragic.  I would so much have liked to run 640x480 in 16bit on the TFT
> and 1024x768 in 256 colors on an external CRT. :(  Is that doable with,
> lets say, Windows 95?

1024x768 in 256 colors on an external CRT should be doable.  I don't
have a monitor so I haven't tried.  I know the AcceleratedX drivers
are capable of doing it.

Tell me if you can get any of the 16-bit Linux drivers working. I use
Win95 right when I need to work in 16-bit mode while still preserving
Unix long-filenames.  Win95 sucks up far too much disk space and RAM
for the marginal improvements it gives me over Win3.1.  I'd love to
dump it if I could do my 16-bit color work in Linux.
--
John H. Kim            There are only two industries that call their
jokim@mit.edu          customers 'users,' and one of them is illegal.
---------- End Forwarded message ----------

Since then, Bjoern reports he's gotten the latest XFree86 alpha driver
to work in 16-bit and 24-bit modes.  The 16-bit is displaced by about
40 pixels on the LCD, and the 24-bit mode flickers, but they work for
him.

I have not been able to get it to work.  It comes up, doesn't lock up
the graphics like it used to, but I get a blank screen.  If I switch
to a terminal session and back, I can see the X desktop for an instant
before it goes black again.  So it's working, it's just not displaying
properly.  I haven't had time to figure out what the problem is, and
all my mail to Bjoern has bounced.

If you get it to work, I'd love a copy of your XF86Config file.
--
John H. Kim       "I stop for red traffic lights" -- bumper sticker 
jokim@mit.edu     commissioned by the City of Boston as part of a
MIT Sea Grant     campaign to shed its reputation for bad drivers.