Macmini (2009) mini displayport as boot screen

Hi, not really a question, more of a difficult to find solution:

If you have a macmini (mine is early 2009), and can't get to the boot screen, but it boots to OSX on it's displayport connection, chances are that your monitor (mine a brand new 4k samsung) is sporting a DP 1.2 connection. If you can drop the monitor to DP 1.1(I could with mine), then you may have more success....

Solution from: https://forums.macrumors.com/threads/boot-screen-on-4k-display-over-displayport.2030659/

Basically, it seems the boot firmware/graphics card combination are not aware of DP 1.2, and so you just get a blank screen - until OSX launches. This makes it quite hard to swap boot disks etc.

If I had found this solution earlier, I would have save the cost of a mini-DVI to HDMI adaptor and HDMI cable I just ordered!

Hope this is helpful to someone else,

Simon