The detailed support document released by Apple for its new range MacBook Pro reveals that the bandwidth of PCI Express 3.0 via Thunderbolt ports on its new 13-inch MacBook Pro with touch bar is limited to two ports on the left.
Although the four ports on the 13-inch MacBook Pro with Thunderbolt Bar Touch 3.0 connectivity features, both in sufficient quantity reduces the bandwidth of PCI Express. This means that in these two ports, the performance of devices that require high bandwidth may be limited. Therefore, it is recommended that high performance devices can connect to ports 3.0 / Thunderbolt USB-C on the left.
The other two models of MacBook Pro that Apple unveiled last week - the 15-inch MacBook Pro with Touch Bar and 13-inch MacBook Pro without touch bar - offer full-bandwidth PCI Express in its Thunderbolt port 3.
Late-2016 MacBook Pro models vary slightly in the data speeds they provide to each Thunderbolt 3 port.
MacBook Pro (15-inch, Late 2016) delivers full Thunderbolt 3 performance on all four ports.
MacBook Pro (13-inch, Late 2016, Four Thunderbolt 3 Ports) supports Thunderbolt 3 at full performance using the two left-hand ports. The two right-hand ports deliver Thunderbolt 3 functionality, but have reduced PCI Express bandwidth.
MacBook Pro (13-inch, Late 2016, Two Thunderbolt 3 Ports) delivers full Thunderbolt 3 performance on both ports.
The Thunderbolt 3.0 ports also allow daisy-chaining so you can have multiple devices connected to your new MacBook Pro from just one port. For example, you can connect one of LG’s new 4K or 5K monitor with the new MacBook Pro which in turn will also charge the laptop. The USB ports on the monitor can then be used to connect external storage devices or peripherals.
Additionally, all the USB-C ports on the new MacBook Pro lineup offer USB 3.1 Gen. 2 connectivity meaning that they are capable of providing transfer speeds of up to 10Gb/s. Any of the available USB-C ports can also be used to charge the MacBook, and if you attach multiple chargers to the laptop at once, it will only pull power from the highest rated charger.