4 USB3 ports, 1 USB-C port, SD card reader, gigabit ethernet, audio ports, HDMK 4K port!
2012 MBP Retina — USB3 Performance
I tested USB3 using the 480GB OWC Mercury Elite Pro Mini.
The MacBook Pro 15" and MacBook Pro 15" with Retina Display perform the same with USB3.
The results show that the USB3 ports offer about 8-12X the performance of the USB2 ports found on older MacBook Pros — a compelling difference. The speed blows-away the sluggish Firewire 800 port on the older MacBook Pros by a real-world factor of 3-7X. That’s a huge gain rarely seen with any upgrade.
While these read/write speeds on USB3 are not as fast as with an internal SATA 6G SSD, they easily exceed the performance requirements of all but a few extremely demanding programs.