I bought one of these (an i7 600) based on the positive review, and a quick check in Ark to make sure it'd do 5k@60Hz over DP. But it's only driving my 5k2k screen at 30Hz or 6bit colour. I tried a bunch of different driver versions & enabling DSC in the registry, but no joy.
Has anyone had luck driving a >4k hi-res display with one of these? Otherwise I guess I'll buy a 10Gbe card & it'll be my new VM host.
So after poking around in the service manuals I figured this out.
The onboard displayport 1.4 ports only do HBR2, so they're only useful for 4k screens.
You need to buy a flex-io v2 displayport option card, which supports HBR3, to drive a 5k screen.
I bought the DP option card for $15 off AliExpress, and I now have 5k2k @ 8 bits @ 60Hz.
Since this is for desktop use, I've used a 2.5Gb USB adapter, which is happily chugging along at full speed. I guess I'll try to sell the 2.5Gb flex-io card.