Emc vs modern lcd monitors
alexdeucher at gmail.com
Mon Aug 15 15:34:00 PDT 2011
2011/8/15 gene heskett <gheskett at wdtv.com>:
> On Monday, August 15, 2011 06:07:09 PM Alex Deucher did opine:
>> 2011/8/15 gene heskett <gheskett at wdtv.com>:
>> > On Monday, August 15, 2011 04:20:49 PM Mark Wagner did opine:
>> >> On Sat, Aug 13, 2011 at 05:50, gene heskett <gheskett at wdtv.com> wrote:
>> >> > Greetings all;
>> >> >
>> >> > One of the problems that was confusing me recently is that I had
>> >> > replaced the old samsung crt monitor with a much newer cheap AOC
>> >> > lcd that runs at 1360x724 at best, but under the vesa driver on an
>> >> > ati x1650 video card, it apparently is running in 1024x768. آ This
>> >> > results in a pixel that is far from square unless I use a button
>> >> > on the monitor which shrinks the display sideways, leaving 2" wide
>> >> > black stripes on the sides.
>> >> >
>> >> > From Xorg.0.log:
>> >> >
>> >> > (II) VESA(0): SAMSUNG: Using hsync range of 30.00-81.00 kHz
>> >> > (II) VESA(0): SAMSUNG: Using vrefresh range of 55.00-75.00 Hz
>> >> > (II) VESA(0): SAMSUNG: Using maximum pixel clock of 90.00 MHz
>> >> > (II) VESA(0): Not using mode "1360x768" (no mode of this name)
>> >> > <---native
>> >> Looks to me like the server is telling you it doesn't know how to
>> >> generate a resolution of 1360x768. If this was a CRT, I'd say to
>> >> provide a custom modeline in the xorg.conf file. Since you've got a
>> >> LCD, I don't know if this is the correct solution or not.
>> > None of my machines have an xorg.conf with a sample modeline for that.
>> > Could someone post an example I could try please?
>> > Or even better, are there docs someplace that would describe how to do
>> > that? I just looked at the modeline description in a man xorg.conf,
>> > and that lacks the specifics I'd need to make a quasi-intelligent
>> > first guess.
>> The problem with vesa is that you are limited to standard vesa modes
>> that are implemented in the vbios. You cannot define arbitrary modes.
>> For that you need to use a real driver specific to your video chip.
> I was afraid of that Alex. And I tried some Modelines suggested on the EMC
> mailing list & got thrown under the bus just as it was leaving. This
> application that must run, is a realtime application with a base loop of
> its i/o running every 20-40 u-secs. _NO_ "real" driver allows that,
> wrecking carving of parts in wholesale numbers because the IRQ's that drive
> this apps base thread can be locked out by the "real" driver for intervals
> in excess of 100 milliseconds. The 'vesa' driver is the only driver that
> allows the base thread to keep some semblance of a steady beat.
> This particular card is an ATI X1650. Does it perchance have an available
> vesa bios update that would add some of the 16x9 modes like this?
Not likely. I don't think vesa ever officially added any 16:9 modes
as standard vesa modes. Have you tried turning off acceleration?
Option "NoAccel" "True"
in the device section of your xorg.conf. That should significantly
reduce the number of irqs generated.
More information about the xorg