Your GPU has 4 display ports.
To use DVI, you have to use a converter, be it a passive or active one, but it has to be there.
Display port, depending on the version, supports(from gpu spec):
- Maximum DisplayPort 1.2a resolution 4096x2160
- Maximum DisplayPort 1.1 resolution 2560x1600
DVI supports, from wikipedia:
- Example display modes (single link):
- HDTV (1,920 × 1,080) @ 60 Hz with CVT-RB blanking (139 MHz)
- WQUXGA (3,840 × 2,400) @ 17 Hz (164 MHz)
- Example display modes (dual link):
Based on these three informations, I conclude that:
Your GPU is fine, and
Your converter is likely at fault, because either
a) it uses DP version 1.1 which doesn't support 4k at 30Hz
b) it uses DVI single link which doesn't support 4k at 30Hz
Thanks for that info. The DisplayPort-to-DVI converter I'm using is a Dell P/N 023NVR (also branded BizLink). Much more expensive powered converters are available, so it's quite possible that this Dell converter doesn't support 4K/30Hz. As I mentioned, the cable I was using was single-link only, so I could have two problems here.
In the mean time, I was able to define a custom mode in Radeon/FirePro settings. 3840×2160 at ~19Hz so the pixel clock is low enough to allow use with a single-link cable.
Replying to my own posting... it turns out the DVI cable I was using was single-link only (the pins used for the second link are not present in the connectors). So I'll try to obtain a dual-link DVI cable and that will most likely solve the problem.