 In April 2012 Asus revealed a revision of the two original Zenbooks , this time based on the Ivy Bridge microarchitecture . The model numbers were UX21A and UX31A for the 11 and 13 inch models respectively but are more frequently referred to as Zenbook Primes . Changes made to the original included the aforementioned update to Ivy Bridge processors and the introduction of the corresponding <unk> chipset bringing native USB 3 @.@ 0 , 1920 × 1080 IPS displays for both models , an Intel <unk> Wi @-@ Fi controller , an improved trackpad and new plastic keyboard with backlighting . The new screens were highly praised by reviewers when considering brightness , contrast ratio , viewing angle and colour accuracy , the improvements over previous models being put down to the switch from TN to IPS displays . The UX21A has contrast ratio of 939 and the UX31A achieved 1085 , giving it the highest resolution and contrast ratio of any ultrabook at the time of release . The improved keyboard also garnered praise for the increased backlighting and improved key travel while the Intel Wi @-@ Fi controller was found to perform better than the Qualcomm used in the first generation of Zenbooks . The Zenbook Primes still received some criticism : the latest version of the trackpad was acknowledged as an improvement over the original Zenbooks , but still irritating , and the sound quality was found to be worse than that with the first generation . Despite these issues , the overall reaction was positive : the UX31A was called " today 's best ultrabook " and " the best ultrabook out there " at the time of release . 
