[ltp] external monitor is blurred!

[Alex Deucher]

On Thu, 23 Dec 2004 02:47:56 +0100, Andr=E9 Wyrwa <a.wyrwa@gmx.de> wrote:
> Hi,
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> On Mi, 2004-12-22 at 14:26 -0700, Ben Pearre wrote:
> > I finally searched the archives and set up my R40 to talk to an
> > external monitor (Dell 2000FP flat panel).  The monitor takes digital
> > input, so I'm very sad that the Thinkpad doesn't have a DVI out, and
> > this is indeed a problem.
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> Yepp, seems that DVI is supported starting from the 50s of R series
> only.
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> > In anything over 1024x768 the monitor only gets a fuzzy, shimmering
> > image.  Not unusable, but very far from crisp: looks like a really
> > cheap analog monitor.  And the default X background ("stipple")
> > shimmers unbearably in horrible vertical stripes.
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> Especially the latter one is a typical sign of bad AD conversion and the
> higher the resolution, the more likely the effect is to show up.
> Usually the effect (moving/shimmering stripes, blurry image) should not
> be homogenic throughout the whole display, but should rather be more
> intense in some parts and in other parts the picture should look quite
> ok.
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> Did you try playing with the Dells phase settings? The autoadjust
> function of such monitors often doesn't deliver the best results.
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> > I don't have much spare computer equipment here, so I can't isolate
> > the component that's causing the problem.  But I assume it's at least
> > one of:
> >
> > * Dell uses cheap a crappy ADC in the monitor
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> Probably not as good as a NEC one, but the Dell ADC should get better
> results than you describe - if you didn't get a faulty model.
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> > * The analog monitor cable is poor (it's thinner than many I've seen
> >   and may be unshielded or poorly shielded but it does have the
> >   ferrous lumps at both ends).
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> That sounds more likely. It is really important to use a good, shielded,
> short-as-can-be monitor cable with a 1600x1200 TFT on VGA since the
> display will have enough problems with the AD conversion even of a
> perfect signal at this resolution. Maybe you can borrow a better one
> from a friend and try with that.
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> > * The Thinkpad has a crappy DAC that doesn't like high resolutions
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> Also unlikely.
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The DAC is included in the radeon package.  Although perhaps ibm used
crappy circuitry to connect the chip to the output, but that's
probably unlikely.

Alex

> >   (how do I find out what the refresh rate is?
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> cat /var/log/Xorg.0.log | grep "*Mode"
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> Or run xvidtune and look at what it shows you.
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> >   Does anyone have a ModeLine that lowers it?)
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> According to the specs the Dell should be fine with 60Hz.
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> >   /var/log/XFree86.x.log suggests that I'm
> >   running at 60 Hz, but I do get "(WW) (1600x1200,Dell) mode clock
> >   162MHz exceeds DDC maximum 160MHz" --- is this bad?
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> That might be bad indeed. According to this page...
> http://support.jp.dell.com/docs/monitors/2000fp/English/specs.htm
>  ...the 162MHz pixelclock mode is the only 1600x1200 preset mode of the
> monitor. You might try adding "NoDDC" "true" to your device section, but
> then you might need to provide a modeline.
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> > * The X software is doing something funny
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> X is always doing something funny. Its part of it's nature.
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> > Can anyone here answer at least for the third and fourth bullets?  Is
> > there a non-DDC modeline that works better?
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> You can try figuring one out by disabling DDC in general and fiddling
> with xvidtune. But don't blow your display.
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> Andr=E9.
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>