When constructing a modeline for use with the Chips and Technologies driver you'll needed to considered several points
Chips later than the ct65540 are capable of supporting Hi-Color and True-Color modes. These are implemented in the current server. The clocks in the 6554x series of chips are internally divided by 2 for 16bpp and 3 for 24bpp, allowing one modeline to be used at all depths. The effect of this is that the maximum dot clock visible to the user is a half or a third of the value at 8bpp. The 6555x series of chips doesn't need to use additional clock cycles to display higher depths, and so the same modeline can be used at all depths, without needing to divide the clocks. Also 16/24 bpp modes will need 2 or 3 times respectively more video ram.
Many DSTN screens use frame acceleration to improve the
performance of the screen. This can be done by using an external
frame buffer, or incorporating the framebuffer at the top of video
ram depending on the particular implementation. The Xserver assumes
that the framebuffer, if used, will be at the top of video ram.
The amount of ram required for the framebuffer will vary depending
on the size of the screen, and will reduce the amount of video
ram available to the modes. Typical values for the size of the
framebuffer will be 57600 bytes (640x480 panel), 90000 bytes
(800x600 panel) and 147456 bytes (1024x768 panel). For systems
with external framebuffers the option "ext_fram_buf
" can be
used to make all the vram available to video memory.
The H/W cursor, and fill operations currently allocate 2kB of the video ram for there own use. If this is not available these functions will automatically be disabled.
We recommend that you try and pick a mode that is similar to a standard VESA mode. If you don't a suspend/resume or LCD/CRT switch might mess up the screen. This is a problem with the video BIOS not knowing about all the funny modes that might be selected.
For LCD screens, the lowest clock that gives acceptable contrast and flicker is usually the best one. This also gives more memory bandwidth for use in the drawing operations. Some users prefer to use clocks that are defined by their BIOS. This has the advantage that the BIOS will probably restore the clock they specified after a suspend/resume or LCD/CRT switch.
The ct655xx driver is capable of driving both a CRT and a flat panel
display. Generally most modelines that work with CRT's will also work
with the ct655xx driver. If the "use_modeline
" or
"fix_panel_size
" options are not specified, only the clock,
polarities, vertical and horizontal sizes are used in the mode calculations
on an LCD. Hence a mode like
Modeline "640x480@8bpp" 21.000 640 0 0 0 480 0 0 0
will often be sufficient for a laptop screen. Just program the zeroed values above to those you would use for a CRT. It should also be noted that flat panels often prefer dot clocks that are much slower than CRT's. Below you'll find listed a set of modelines that are in use of a variety of machines. These can be used as starting points for new modelines.
Modeline "640x480@8bpp" 21.000 640 688 704 776 480 480 481 486 Tested on a Sharp PC3020, (640x480 DSTN, 65545A1, 512kByte) Modeline "640x480@8bpp" 16.000 640 688 704 776 480 480 481 486 Modeline "640x480@16bpp" 16.000 640 688 704 776 480 480 481 486 Modeline "640x480@24bpp" 16.330 640 664 760 800 480 490 502 525 Tested on a Toshiba Satellite T2135CS (640x480 DSTN, 65545??, 1MByte) Modeline "640x480@8bpp" 25.175 640 664 760 800 480 491 493 525 ModeLine "640x480@8bpp" 28.322 640 680 720 864 480 488 491 521 Modeline "640x480@16bpp" 38.000 640 648 668 808 480 490 502 525 Modeline "640x480@24bpp" 23.000 640 648 756 809 480 490 502 525 Tested on a Toshiba 400CDT, (640x480 TFT, 65546 1Mbyte) Modeline "800x600@8bpp" 40.000 800 840 968 1056 600 601 605 628 Modeline "800x600@16bpp" 36.000 800 840 968 1056 600 601 605 628 Tested on a Sager Narval86 (800x600 DSTN, 65548, 1Mbyte) Modeline "1024x768@8bpp" 65.000 1024 1032 1176 1344 768 771 777 806 Modeline "1024x768@16bpp" 65.000 1024 1032 1176 1344 768 771 777 806 Tested on a Toshiba 720CDT, (1024x768 TFT, 65550, 2Mbyte)
Note that there are some machines that are known to need the panel timings
reprogrammed for use with XFree using the "use_modeline
" option.
One such machine is the "Prostar 8200
" with a 640x480 TFT. For
this machine a modeline that is known to work is
Modeline "640x480@8bpp" 25.175 640 672 728 816 480 489 501 526 Modeline "640x480@16bpp" 25.175 640 672 728 816 480 489 501 526 Tested on a Prostar 8200, (640x480, 65548, 1Mbyte)
Also there are some machines that are known to report the LCD panel size
incorrectly. The correct panel size can be forced into registers from the
modeline values using the "fix_panel_size
" option. Two machines
that are know to need this option are the HP OmniBook 5000CTS and the
NEC Versa 4080 800x600 TFT machines. A modeline that is known to work
with the OmniBook in conjunction with the "use_modeline
" and
"fix_panel_size
" options is
Modeline "800x600@8bpp" 28.322 800 808 848 936 600 600 604 628 Tested on a HP OmniBook 5000CTS (800x600 TFT, 65548, 1Mbyte)
The NEC Versa 4080 just needs the "fix_panel_size" option.
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