Modelines and DVI-D output

Alex Deucher alexdeucher at
Fri Feb 25 06:33:05 PST 2005

On Fri, 25 Feb 2005 14:19:27 +0100, Roland Scheidegger
<rscheidegger_lists at> wrote:
> Morten Sylvest Olsen wrote:
> > Hi list..
> >
> > Is anybody here a world champion in modelines? :) How exactly does
> > modelines make a difference when driving TFT monitors over a DVI-D link?
> > Obviously the different timings related to beam retracing etc. have no
> > physical meaning.
> >
> > The reason I am asking is that I have a TFT monitor that simply refuses
> > to show anything at all. The monitor is a Barco E-3220 which is a
> > "medical" type greyscale monitor with resolution 1536x2048. The monitor
> > supports EDID and returns a modeline, which X uses but the monitor is
> > never able to sync on the signal.
> >
> > Modeline "1536x2048"  200.00  1536 1564 1580 1584  2048 2088 2120 2152
> >
> > The graphics board is an ATI FireGL V7100 (using the binary driver
> > though, but don't know if that really matters)
> >
> > I would not put it past them to return crap in the EDID, since they try
> > to sell hideously overpriced "medical" graphics board together with
> > their monitors.
> >
> > A previous monitor of theirs return EDID data 2048x1536:
> >
> > Modeline "2048x1536" 200.4  2048 2096 2156 2152 1536 1537 1557 1558
> >                                            ^^^^
> > where h_blank_end is before h_sync_end. That *must* be bogus, right?
> >
> > Hope somebody is able to shed a bit of light on this.
> I'm no expert on modelines, but 200Mhz pixel clock is only possible with
> dual-link dvi. Your card has one dual-link and one single-link dvi
> connector, thus you need to use the correct one.
> I have no idea if fglrx (you'd need to ask ati about that) or the
> open-source radeon driver can actually handle the external dual-link
> tmds transmitter the fglrx cards have.

there is a duallink enable bit and probably some other stuff that
needs to happen on the external tmds controller.  The problem is that
right now the the tmds controllers are hardcoded to crtcs, so you'd
have to use dualhead to enable the second tmds controller properly. 
I've got a patch I've been working on to separate out the crtc and
output handling, you may have some luck with (still doesn't deal with
dual-link, but that shouldn't be too hard to add).

it's still pretty rough and unforuntately at the moment, I don't have
a dual digital setup to test with, but I plan improving it.


> You also _might_ be able to drive the monitor with a single-link dvi
> connector, if you use a modeline with 165Mhz pixel clock (this would
> reduce the vertical refresh rate to around 45Hz or so, it depends on the
> monitor's input logic if it accepts that or not).
> Roland

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