Hmm, actually TomsHardware had it running at 60hz with two HDMI cables, but the article points out the challenge is the display card. The spec on the ASUS glass is 8 mS pixels, you can only change a by refreshing the screen, if you are changing them every 8 mS you are refreshing the screen every 8 mS which is half of 16 mS or 120Hz. Typical 60Hz displays have 12mS pixel change times.
Now I'll certainly concede that running 30bits of color per pixel to a 3840 x 2160 screen at 120hz will require 3.7GBs of bandwidth but each display port can provide 2.16GBs [2] for a total of 4.32GBs across both panels.
It will be interesting once the "4K generation" of graphics card hits the street to see what this monitor can do.
[1] "Asus’ $3500 PQ321Q is one of the only 4K screens capable of 60 Hz. But in order to achieve that refresh rate, you’re forced to run either one DisplayPort or two HDMI cables between your PC and the monitor." -- http://www.tomshardware.com/reviews/pq321q-4k-gaming,3620.ht...
[2] "The DisplayPort connector can have 1, 2, or 4 differential data pairs (lanes) in a Main Link, each with a raw bit rate of 1.62, 2.7, or 5.4 Gbit/s per lane with self-clock running at 162, 270, or 540 MHz. Data is 8b/10b encoded where each 8 bits of information is encoded with a 10 bit symbol. So the effective data rates after decoding are 1.296, 2.16, and 4.32 Gbit/s per lane (or 80% of the total)." -- http://en.wikipedia.org/wiki/DisplayPort
Now I'll certainly concede that running 30bits of color per pixel to a 3840 x 2160 screen at 120hz will require 3.7GBs of bandwidth but each display port can provide 2.16GBs [2] for a total of 4.32GBs across both panels.
It will be interesting once the "4K generation" of graphics card hits the street to see what this monitor can do.
[1] "Asus’ $3500 PQ321Q is one of the only 4K screens capable of 60 Hz. But in order to achieve that refresh rate, you’re forced to run either one DisplayPort or two HDMI cables between your PC and the monitor." -- http://www.tomshardware.com/reviews/pq321q-4k-gaming,3620.ht...
[2] "The DisplayPort connector can have 1, 2, or 4 differential data pairs (lanes) in a Main Link, each with a raw bit rate of 1.62, 2.7, or 5.4 Gbit/s per lane with self-clock running at 162, 270, or 540 MHz. Data is 8b/10b encoded where each 8 bits of information is encoded with a 10 bit symbol. So the effective data rates after decoding are 1.296, 2.16, and 4.32 Gbit/s per lane (or 80% of the total)." -- http://en.wikipedia.org/wiki/DisplayPort