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The relevant part of my system is straightforward - a Radeon R9 370 card with HDMI + DisplayPort output. The monitor is a 4K (3840 x 2160) Dell UltraSharp UP3216Q with HDMI 2.0 and DisplayPort connectors.

My underlying problem is the well-known issue that when the monitor turns off, or the second monitor changes, my windows all move around. I've tried a number of fixes but none work well. Those that do, work by forcing the EDID values in Windows, which means if I do disconnect or change the monitor (as opposed to just turning it off), it still thinks there's a 3840 x 2160 attached, when it should resize to a smaller screen :)

My solution is to move to a pass-through EDID emulator to solve this properly. The intended effect is that if I turn the monitor off but the cable is still connected, Windows will see it (due to the emulator) as still connected, and windows won't move round. But if the cable itself is unplugged, the EDID emulator will be disconnected with it and Windows will see a change of monitor or loss of monitor instead, which is ideal behaviour. That should fix it, if the EDID emulator works as expected.

  • Important point to note: The EDID emulator needs to be a "pass through" type - one that has male and female ports, "listens" to the monitor's own EDID, and remembers/emulates it when the monitor isn't powered on. "Headless", "dummy" or "ghost" EDID emulators are the wrong type. Those types are used to fake a monitor totally, to a computer that doesn't have any monitor at all, so that the graphics card will be fully used in calculations and remote desktop work. A headless/dummy EDID emulator only have one port, a bit like a USB stick, and won't do the job I need; it needs to be pass-through.

The problem is that 3840 x 2160 DisplayPort pass-through EDID emulators are either extremely new on the market, or not on the market yet, and I want this now :)

My proposed solution is to notice that my monitor has HDMI 2.0 as well as DisplayPort. That means I could feed it 3840 x 2160 on the HDMI port and use an HDMI EDID emulator instead. Unlike DisplayPort, I'm pretty sure that 3840 x 2160 HDMI pass-through EDID emulators are much easier to find on the market and cheaper too, and this would solve my Windows problem equally well.

My adapter's HDMI output is already in use, so I would need to get a DisplayPort to HDMI adapter as well. The connection would be:

  • (R9 370 adapter Displayport) -> (DisplayPort cable) -> (DP to HDMI 2.0 adapter) -> (HDMI 2.0 pass-through EDID emulator) -> monitor

I'm guessing I will need an HDMI 2.0 emulator and adapter for this resolution. My questions are the obvious ones:

  1. Will an HDMI EDID pass-through emulator work correctly "behind" a DP to HDMI adapter?
    (I can't think of a reason it wouldn't but you know how compatibility and media changing can be. I could be wrong.)
  2. Can DP to HDMI adapters, and HDMI EDID emulators be found, that work at 3840 x 2160 @ 60 Hz? 2. Will HDMI 2.0 handle it? Are all adapters/emulators pretty much equally reliable for this kind of need, or should I go for a specific buty more expensive brand?
    (Cheaper is best if possible!)
  3. If it'll work, what would be a recommendation for the cheapest "known good" adapter and emulator I should get?

I'm in the UK and usually buy on Amazon or EBay.

  • Is there not a way to just prevent the monitor from turning off so you don't have to deal with the EDID spoofing? I can't speak to EDID working, but regarding HDMI 2.0, it's dependent on if your card has DisplayPort 1.3, since most adapters use passive DisplayPort++. Unfortunately, there's not enough info on the R9 370 online for me to figure out if it does, so you'll need to do it on your own. – JMY1000 Jun 14 '18 at 11:37
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Chaining worked, but I had to check with the manufacturer for model numbers and to confirm it would work. Their tech team kindly tested it for me, to check that the HDMI EDID adapter would work behind a DP to HDMI adapter, and told me the exact parts they had used to make it work.

The parts I used were from Lindy, and were a 41068 DP1.2 to HDMI 4k 60Hz converter, with a 32113 HDMI 2.0 EDID adapter plugged into it. Initially I got the adapter the wrong way round - be careful if you use these parts, the "male" (plug) end of the HDMI EDID adapter faces the computer, the "female" (socket) end faces the monitor.

Obviously there are probably other people making these; at this time there isn't much choice but that's likely to change.

They're working absolutely fine, rock solid, on both my HD TV and my 4k monitor.

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