Just released earlier tonight, Apple's OS X Mavericks 10.9.3 beta appears to have built-in support that enables all compatible 4K displays to be set at a "Retina" resolution, with an option for 60Hz output. The compatibility was first discovered by Twitter user @KhaosT, and was tested with both the Late 2013 Retina MacBook Pro and redesigned Mac Pro in conjunction with Dell's UltraSharp 24 Ultra HD Monitor. To this point, OS X compatibility with 4K displays has been known to be
