adx
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Dual link DVI possible on Pi 4?

Tue Aug 13, 2019 8:39 am

Long shot question, but I'd like to drive some 2560*1600*60 monitors (Dell, HP etc) and that is the only native mode they do. They refuse to do anything like 30p over single link / HDMI. When I saw the two HDMI connectors I thought "oooh - what if?". Hence my first post!

itimpi
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Re: Dual link DVI possible on Pi 4?

Tue Aug 13, 2019 12:06 pm

The monitors have DVI inputs so will probably ‘just work’ with an appropriate cable.

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HawaiianPi
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Re: Dual link DVI possible on Pi 4?

Tue Aug 13, 2019 12:18 pm

The Raspberry Pi 4B can drive monitors up to 4K resolution, so you should be able to get it working.
(hdmi_group=2 and hdmi_mode=77 is 2560x1600 60Hz)
You'll need a micro HDMI to dual link DVI cable or appropriate adapters.

Older models only support up to 1080p, so less likely (especially if they are as finicky as you say).
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?

adx
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Re: Dual link DVI possible on Pi 4?

Tue Aug 13, 2019 1:29 pm

The problem is it'd need all the dual-link pairs, which HDMI doesn't have. What I had in mind was taking the TDMS pairs for RGB from HDMI2 and combining with HDMI1, using its clock and whatever else is necessary. A hacked up Y cable, basically. A cunning driver would be able to present data in a format the monitor can eat - it seems that it sends every second pixel on a different link which is a bit tricky to mangle. Would be nicer if it was half and half - for side by side display on the one screen! I'm guessing it would only be practical with some trickery that exists as support on the SoC specifically for dual-link DVI.

One advantage is that all the 'old' 30" monitors of this type have that one mode, so one hack would do all. I gather it can be converted using an active HDMI to displayport adapter, then displayport to dual link DVI, but cost of each of those devices probably exceeds an RPi.

I've used an Rpi2 for years as a thin client driving a 1920*1200*60 screen no problem (well, the odd green flash). It's only 16 bit colour, but anything useful over RDP (anything but video) seems to dither colours nicely. I so badly wanted dual screen, and now that seems to be a reality (could never get true dual screen with VGA666). But greed has kicked in, it'd be nice to run these big monitors off something small and modern, rather than a full-size PC (even a SFF PC is not easy to get dual link DVI cards for).

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