Enforcing video output without monitor detection

[fse]

I tried to use a 27' iMac (Late 2009) as external monitor for a Windows 7 laptop using a Fujitsu Port Replicator (PR08). iMac supports a Mini-Displayport input with max. 2560x1440 pixels (in "Target Display Mode"), while PR08 provides a Displayport output (also with 2560x1440 pixels). I connected both with a MDP to DP cable. According to specs, it should work - but it doesn't.
Neither does Displaylink driver (latest version 7.7) detect iMac as monitor nor does iMac switch into "Target Display Mode" (via CMD-F2 shortkey). It seems, that each side requires the other side to do the first step! iMac only switch into monitor mode, if it detects a valid video signal. Displaylink provides only a video signal, if it detects a monitor.
My question: Can Displaylink drivers be forced to provide a video signal, even if no monitor is detected? It seems, that original Windows graphic drivers would support this, if my laptop would have a Displayport output.

Thanks.

[JamesH]

Hi,

DL-1xx based devices don't require a monitor to be present, DL-3xxx & DL-5xxx do.

Thanks,
James

[fse]

Hi James,

thanks for your reply. Unfortunately, DL-1xx does not support the required monitor resolution. From technical point of view, DL-3xxx & DL-5xxx should be able to provide a signal without a previous monitor detection. It's just a matter of driver implementation. I hoped, that there is kind of hidden debug feature, in order to omit this limitation of the driver GUI.

To me this means, that I have to sell again my new DisplayLink hardware in order to buy a laptop with native DisplayPort output based on an Intel GPU. Because Intel/Windows drivers support manual graphics configuration. That's too bad.