Force Graphics Output with no EDID data

[Falki]

I’m looking for a solution to use a monitor that is not able to send the EDID data correctly.

I know, I’m stretching the limits with my use case, however, I hope somebody knows how this is supposed to work.

I’ve got a secondary display that uses a 20m high quality HTMI cable to connect to the CPU. However, with this cable, the EDID data can not be read properly anymore, on the other hand, the HDMI data would display just fine.

I’ve used an EDID emulator (like Delock  EDID Emulator HDMI - HDMI Adapter) to test the HDMI part and a I2C analyzer to check the EDID data. With the EDID emulator everything is fine, however, in the real environment, I’m not able to use this device, as there is absolutely no space to put and fix it property there.

I was trying to use EDID_Override and Default_Monitor with no success and I stared to wonder how this is supposed to work at all.

By the way, this is the same behavior on Windows 7 and Windows 10 (embedded versions). The CPU is an Intel Atom E3845 with integrated graphics card using the Baytrail Intel HD Graphics driver, versions 36.15.0.1127 or 10.18.10.5161 respectively (and yes, I know, it’s not supported anymore).

I had the opinion, in case there is no EDID data available but the hot plug detect (HPD) signal active, Windows would just use some default resolution such as SVGA or similar (I’m almost sure this was the case in Windows XP). However, the monitor is not even showing up in the device manager / control panel. Therefore I’m not able to adjust the resolution manually.

The I2C logs show, that the EDID data is being requested, but the header data is corrupt due to the cable length. After this, Windows just shows nothing, no event log, no secondary monitor, nothing I could get my hands on.

As mentioned, I’ve looked into EDID Override, put meanwhile, I think this only works if the EDID data is wrong and the resolution (or other parameters) should be corrected. If there is no vendor received, the override seems not to work.

I also looked into the Default_Monitor where a BAD_EDID is defined. However, whatever I tried to do, there had no effect.

Therefore my two question:

• How is this supposed to work in Windows nowadays?
• Is the a way to force Windows or the graphics card to enumerate (switch on) the monitor permanently or if the hot pug signal is detected, even there is no valid EDID data received on this port, without using any additional external hardware?

Many thanks,

Martin