Wonder if I find a DVI Dual Link to HDMI cable if I can at least manually get the 2560x1440 to work even if Auto Detect does not seem to be working for me.
Wait, so manually adding the modes doesn't let it work? What do you get? A blank screen? Or are half the pixels missing (which is what happens in dual-link mode)?
Try experimenting with adding +RB/-RB to the modes. You'll find this as "Reduced Blanking" in ScreenMode prefs.
Hans, you mention forget the DVI Dual Link cable.... does this mean I just will max out at 1920x1080 then even though this display on Mac or Linux works fine in 2560x1440 via HDMI cables?
No. As I said, the latest drivers support HDMI's higher pixel clocks when an HDMI 1.3+ monitor is detected. AFAIK, nobody has made a dual-link HDMI monitor (which uses a different size connector), so a dual-link cable will do nothing.
Wll a better video card help?
Your graphics card is UHD capable. I think your problem really comes down to DDC not working. The driver needs DDC to work in order to detect HDMI 1.3+ monitors. Do your other machines auto-detect the monitor and its modes with the same cables?
I assume you've already tried plugging it in to every possible port on the graphics card. There is a possibility that the graphics card ROM's DDC connection table is wrong, resulting in it not working. However, it would be incredibly rare for it to fail on all ports.
Hans