Whereas Apple's new 13-inch MacBook Pros feature integrated Iris Pro graphics, the 15-inch MacBook Pros feature dedicated AMD graphics, resulting in significant performance improvements over previous MacBook Pro models. Ars Technica's Andrew Cunningham found the Radeon Pro 455 graphics chip in particular to be a "significant boost" over the dedicated GPUs available in the 2012-2015 MacBook Pro models, such as the Nvidia GeForce GTX 650M, Nvidia GeForce GTX 750M, and AMD Radeon R9 M370X. MacRumors reports: AMD's Polaris-based Radeon Pro 450, Radeon Pro 455, and built-to-order Radeon Pro 460 GPUs in the new 15-inch MacBook Pro support up to six displays, whereas Intel's integrated GPUs affixed to the logic board can drive a total of three displays. The expanded support enables the new MacBook Pro to drive two of Apple and LG's new UltraFine 5K displays at 60Hz simultaneously. Intel's GPUs can't because, due to bandwidth limitations of the DisplayPort 1.2 spec, the two 5K displays technically function as four displays. This method is known as Multi-Stream Transport (MST). Apple could have used Nvidia's faster Pascal-based GPUs, which support DisplayPort 1.3, but Thunderbolt 3 and most monitors do not support the higher-bandwidth spec yet. In the meantime, Nvidia's GPUs can only drive up to three displays beyond the main MacBook Pro screen -- not enough for dual 5K displays over MST. Apple officially says the 15-inch MacBook Pro offers up to 130% faster graphics performance, and up to 2.5x more computing power per watt, compared to the previous-generation 15-inch MacBook Pro, but those stats are based on the built-to-order Radeon Pro 460 chip that costs between $100 and $200 extra.