The History of USB
Let’s take a look at this history of the USB standard.
iMac 2012 and lateriMac Pro 2017 and lateriPad Pro 2016 and later (with a Lightning-to-USB adapter)Mac mini 2012 and laterMacBook Air 2012 and laterMacBook Pro 2012 and laterMac Pro 2013 and later
USB 1.x
USB 1.1 provided a plug-and-play connection that supported speeds from 1.5 megabits per second (Mbps) to 12 Mbps. USB 1.1 wasn’t a speed demon, but it was fast enough to handle mice, keyboards, modems, and other low-speed peripheral devices.
USB 2
USB 2 was capable of speeds up to 480 Mbps. Top speeds occurred in bursts, but the second generation was a significant improvement. External hard drives designed for USB 2 became a popular way to add storage to your Mac. This improved speed and bandwidth made USB 2 a good choice for other peripheral devices, as well, including scanners, cameras, and video cameras.
USB 3.x
This third generation of the USB standard introduced a new data-transfer method called SuperSpeed (SS), which gives USB 3 a theoretical top speed of 5 gigabits per second (Gbps). In actual usage, a top speed of 4 Gbps is typical, with a continuous transfer rate of 3.2 Gbps. USB 3.x is fast enough to prevent most of today’s hard drives from taking over the connection with data. It’s also fast enough that you can use it with most Serial Advanced Technology Attachment (SATA)–based solid-state drives, especially if the external enclosure of your hard drive supports the USB Attached SCSI Protocol. Raw speed isn’t the only improvement in USB 3. The new generation uses two unidirectional data paths: one to transmit and one to receive. So, you no longer need to wait for a clear bus before sending information. USB 3.1 Gen 1 has more or less the same characteristics as USB 3. It has the same transfer rate (5 Gbps theoretical max), but you can combine it with the USB Type-C connector to provide up to 100 watts of additional power. It can also understand DisplayPort and HDMI video signals. USB 3.1 Gen 1/USB Type-C is the port specification used with the 2015 12-inch MacBook. In other words, it refers to the shape of the port. It provides the same transfer speeds as a USB 3.0 but adds the ability to handle DisplayPort and HDMI video. It’s also the port you plug your AC power adapter into to charge the device’s battery. USB 3.1 Gen 2 doubles the theoretical transfer rates of USB 3.0 to 10 Gbps—the same transfer speed as the original Thunderbolt specification. Some Apple device models combine USB 3.1 Gen 2 ports with the new USB Type-C connector to include recharging capabilities as well as DisplayPort and HDMI video connections. USB Type-C (also called USB-C) is a mechanical standard for a compact USB port that can be used (but isn’t required) with either the USB 3.1 Gen 1 or USB 3.1 Gen 2 specification. The USB-C port has some interesting hallmarks:
You can plug a USB-C cable into your device facing either up or down.USB-C can support more data lanes, allowing data rates up to 10 Gbps and supporting DisplayPort and HDMI video.USB-C can handle more power (up to 100 watts), which is why Apple uses the USB-C port on many of its devices to charge their battery.
Just because a device has a USB-C connector doesn’t automatically mean that the port supports video or Thunderbolt-like speeds. To determine whether the USB-C port on your Mac is USB 3.1 Gen 1 or Gen 2, perform these steps:
USB 3 Architecture
USB 3 uses a multibus system that allows USB 3 traffic and USB 2 traffic to operate over the cabling simultaneously. So, unlike earlier versions of USB, which operated at the top speed of the slowest device connected, USB 3 can zip along even when a USB 2 device is connected. USB 3 also has a feature common in FireWire and Ethernet systems: a defined host-to-host communications capability. Through this capability, you can use USB 3 with multiple computers and peripheral devices at the same time. And specific to Macs, USB 3 should speed up Target Disk mode, an Apple method you use when transferring data from an older Mac to a newer one.
Compatibility
USB 3 was designed to support USB 2, as well. All USB 2.x devices should work when you connect them to a Mac equipped with a USB 3 port. Likewise, a USB 3 peripheral device should work with a USB 2 port, but in truth it depends on the type of USB 3 device.
USB 3 and Your Apple Device
All Mac models after 2012 have USB 3.0 ports. The only exception is the 2015 MacBook, which used USB 3.1 Gen 1 and a USB-C connector. No Mac models had dedicated USB 2 ports because Apple created its own version of that standard, instead, called Lightening. Apple used the standard USB Type-A connector, but the USB 3 version of the connector had five additional pins that supported the high-speed operations of USB 3. So, you must use USB 3 cabling to get USB 3 performance. If you use an old USB 2 cable that you found in a box in your closet, it will work but at USB 2 speeds. In 2016, Apple obliged its fans with one of the most requested additions to iPad: USB 3.0 functionality. The iPad Pro (third generation) has a USB-C port that you can use to connect the device directly to an AC wall outlet or a computer—Mac or Windows-based PC—that has a Thunderbolt or USB-C port for charging. You can also use this port to connect peripheral devices, such as monitors, to your iPad Pro. (Depending on the ports on your computer, you may need an adapter.)
