How can a Mac mini drive 3440 pixels wide display instead of 1920? I've bought a new 21:9 IPS screen with a native resolution of 3440x1440px. The display has only two inputs: 1x DisplayPort which is connected to a workstation and 1x HDMI port which should go to my Mac Mini (Late 2012).

Unfortunately on the Mac, I only get 1920x1080@60hz in the system settings. Probably because HDMI hasn't enough throughput. My plan was to lower the Hz to 30. But this isn't possible. Only 60Hz and 50Hz are selectable under El Capitan.

The Mac Mini has two different outputs. 1x HDMI and 1x Thunderbolt/Mini-Displayport. 

Do I simply need a different hardware adapter to get 3440x1440@30hz on the thunderbolt port using a HDMI&lt;->Mini-Displayport adapter?
Yes. The limitation is in the adapter cable. The one you listed should work well and there are many others now like the cable matters one linked below. 


http://www.apple.com/shop/product/HHLY2ZM/B/belkin-4k-mini-displayport-to-hdmi-cable-2-m-65-ft?fnode=8b
http://www.amazon.com/Cable-Matters-DisplayPort-Thunderbolt-Compatible/dp/B00K0UDJFI