Recently I have been having issues with my Sharp PQ321Q 4K display @ 60hz. Radeon 7970 4k 60Hz Issues by Nicholas Woodhams.
When running OS X 10.10.3 and newer, I wasn't able to get a 60hz refresh rate, which resulted in choppy scrolling and what seemed like a lagging system.
To attempt to solve the problem, I upgraded my graphics card to an NVIDIA GTX 980 running the web drivers. The speed of the UI did improve slightly, but it was still stuck at 30hz and sub-par.
After doing a lot of reading, I narrowed the issue down to the support of MST. In OS X 10.10.3 Apple added support for many new LCD displays including Dell's new 5k display. However they dropped MST support for the Sharp PQ321Q and some other monitors.
If I wanted to upgrade past 10.10.2 at any point, I'd need to replace my monitor with one that supported 60hz with Single Stream Transmission (SST). That's exactly what I did.
Enter the LG 31MU97-B 31" 4K Monitor. It runs at 4096x2160 60hz no problem with the GTX 980 on OS X 10.10.5. No more choppiness.
It's not necessarily better than the PQ321Q, but a lack of 60hz support was a deal breaker for me.
Where the LG 31MU97-B is Better
- The big one. Full resolution @ 60hz with SST.
- More pixels. Runs at 4096x2160 instead of 3840x2160.
- USB 3.0 Hub Built In.
- No Power Brick. (The PQ321Q has a massive one).
Where the PQ321Q is Worse
- Not as bright. I noticed that the brightness was substantially lower. It felt uncomfortably low until I got used to it and lowered the brightness on my side monitors.
- A half inch screen size reduction. This is actually pretty noticeable. I had to increase the font-size on my text editor from 13pt to 15pt.
- Not as beefy. Cords have to run down a thin stand, there's nowhere to hide them.
If you need help getting 4k @ 60hz working, don't hesitate to contact me. Please let me know if this helps you.