The latest OS X Mavericks 10.9.3 build 13D21 comes one week after the last beta was seeded, and Apple once again asks developers to focus on graphics drivers and audio enhancements.
New to both OS X Mavericks 10.9.3 and iTunes 11.1.6 betas is the restoration of iTunes syncing for contacts and calendar data over USB and Wi-Fi, a feature deprecated from the current version of iTunes in favor of Apple's iCloud solution. Combined with the latest iTunes 11.1.6 beta, developers can now sync contact and calendar data on an iPhone, iPad or iPod with a host Mac.
In addition to the iTunes changes, Apple requests developers continue to work on audio and graphics improvements, as well as Safari.
An earlier seed of OS X Mavericks 10.9.3 revealed Apple is planning to enable a so-called "Retina" output mode for users connecting their late-2013 MacBook Pro with Retina display to external 4K monitors. The added feature can be described as a pixel-doubling scaling option that is capable of displaying a desktop at native "Retina" levels over HDMI.
Currently, Retina MacBook Pro owners running OS X 10.9.2 are limited to a maximum scaled resolution of 4,096 pixels-by-2,160 pixels at 24Hz. The refresh rate is also capped at 30Hz for lower resolutions, making animations choppy. With the upcoming maintenance update, output to a 4K display is expected to achieve 60Hz while pixel-doubling.
Developers can download the new beta builds from Apple's Developer Portal or Software Update.