Summary of speed and functions by USB type, which 'even experts are confused'

USB (Universal Serial Bus) has been the standard connection type for computers and most IT devices since 1998 when Apple made a bold decision to use it with its innovative original iMac.

Prior to UBS, there were many types of connections, ranging from ADB to FireWire to SCSI, all with their own variations. 

Like most technology standards, USB is getting faster and faster as new versions are released every few years, and it's a great deal in terms of speed and functionality. Despite being 'universal', there are currently many types of USB, some of which are being phased out in all but the cheapest ones. 

The ideal of universalization is still being pursued and is getting much closer. Before explaining USB speed, let's look at the different types of USB. USB-A, with its rectangular connector, is the most widely used and is still the centerpiece of PCs and devices. The USB-B address was preferred by the printer manufacturer, which fell into a tunnel-like shape. The USB-B mini is still used a lot here and there. Micro -USB to (Micro-USB, micro-USB-B actually) are pesky little connector used in small devices, old and cheap, it seems to be always inserted in the wrong direction each time you try to insert into the slot. There are several clever micro-USBs that can be used on both sides.  Commonly found on external hard drives.

There is also a USB-B micro super speed type. There are 10 pins compared to the 5 pins of the micro-USB. 

USB-C solves the disappointing single-sided use of USB-A and micro-USB with double-sided use, allowing symmetrical rectangular connectors to be plugged in either direction. It is very convenient. Most of the latest laptops, tablets, and phones (except iPhones that use Lightning) have switched to USB-C, and everyone will appreciate it. 

In fact, newer laptops often only have USB-C or Thunderbolt ports. So, if you want to connect your device to a different connector, you'll need a USB-C docking station, Thunderbolt docking station, or a USB-C hub.

USB-C is smaller than USB-A, but has a faster data transfer rate and can deliver up to 100W of power. DisplayPort signals can be sent through cables and connectors such as USB signals, so you can connect an external display if your computer supports it.

Using the alternate mode of USB-C for video (Alternate Mode, also known as 'Alt Mode'), the adapter outputs video from the USB-C port to HDMI and DisplayPort, VGA, and other types of video connectors on the display, TV, and projector. can do. Many modern monitors now have their own USB-C port, which can be connected directly using a USB-C cable. 

Macs don't support Multi-stream Transport (MST), so most are limited to just one external display via USB-C. 4K video via USB-C is also limited to a 30Hz screen speed. An exception is a case of using Caldigit's SUB-C SOHO dock. Separate lanes are used for both video and USB, so it can reach 60Hz. 

Thunderbolt 3 allows multiple external displays on Mac and Windows PCs and supports 4K video at 60Hz. 

USB-C also supports USB Power Delivery (USB PD). When USB 3.1 only supports 15W (sufficient to charge a cell phone, but not enough to power up a laptop), the USB PD delivers up to 100W of power. 

The Apple Lightning connector is similar to USB and can be double-sided like USB-C, but you can only find it on Apple devices and accessories. 

USB speed, various from 12 to 40,000Mbps

USB types are easy to understand because they come in different shapes. USB speed was easy to understand from the start. Megabytes (MB) are eight times larger than megabits (Mb). For easier comparison, USB speeds are listed in megabits per second, megabytes per second, and gigabits per second.  

USB 1.1 (aka Full-Speed) can reach 12Mbps. This corresponds to 0.125MBps.

USB 2.0 (aka Hi-Speed) is overwhelmingly faster than USB 1.1 at 480Mbps or 60MBps. This specification is still heavily used in devices and docking stations. 

USB 3.0 (aka SuperSpeed) has taken the speed to a new level with 5Gbps. This is equivalent to 625MBps or 5,000Mbps. 

Unfortunately, USB 3.0 has diversified due to the confusion of several 3.x variants. Version 3.1 was terribly messy. USB 3.1, released in July 2013, comes in two variants. First, USB 3.1 Gen 1 is at 5Gbps speed, which is the same as USB 3.0 SuperSpeed. And USB 3.1 Gen 2, also known as SuperSpeed+, has a speed of 10Gbps (1,250MBps = 10,000Mbps).  The 10Gbps version was simultaneously known as 'USB 3.1 Rev 2','USB 3.1 Gen 2', and 'SuperSpeed ​​USB 10Gbps'.

USB 3.2 type and speed

USB 3.2 came out to solve this complex problem, but, frankly, it's hard to fully understand. 

USB 3.2 is dedicated to USB-C, not USB-A, and is trapped in the USB 3.1 naming convention, up to 10Gbps. Newer versions of USB often offer more features and higher efficiency power management. But in this article, I'll go into the details of USB 3.2 speed.  

The USB 3.2 specification includes all previous 3.x specifications and provides the following three transfer rates. 

USB 3.2 Gen 1x1 (commonly referred to as USB 3.2 Gen 1): 5Gbps SuperSpeed ​​USB

USB 3.2 Gen 2x1 (commonly referred to as USB 3.2 Gen 2): 10Gbps SuperSpeed ​​+

USB 3.2 Gen 2x2: 20Gbps (2,500MBps) SuperSpeed+ USB. 2x2 means that the bus has 2 lanes instead of 1, so the speed is doubled. 

The USB-C connector has four pairs of pins known as 'lanes' that send and receive data. USB 3.2 Gen 1 (5Gbps) and USB 3.2 Gen 2 (10Gbps) use one transmit lane and one receive lane. USB 3.2 Gen 2x2 utilizes 4 lanes to achieve 20Gbps data rates.

Superior Thunderbolt 4, replacing some Thunderbolt 3

Ignoring Thunderbolt 1.0 and Thunderbolt 2 using the mini DisplayPort connector, the Thunderbolt 3 (T3) looks the same as USB-C, but at 40 Gbps (5 GBps = 5,000 MBps = 40,000 Mbps), it is much faster and performs better. Better 

Thunderbolt provides PCI Express data and DisplayPort functions for hard drives, SSDs, and graphics cards in one cable. 

In addition, since it is a peer-to-peer method rather than a host-to-user (USB), multiple peripheral devices can be connected to the existing connection in a daisy chain method. 

And Thunderbolt 4 (T4) appeared. Mac users won't notice much of the difference between the T3 and the T4, as features or specifications aren't upgraded. But the Windows world tends to focus on a limited version of the T3 that will be replaced by the new T4 certification. 

Guaranteed speed, for example, means that all T4-compatible devices must support at least two 4K external displays or a single 8K display. 

T4 allows for longer cables (T3 provides maximum speeds of up to about 1m before bandwidth loss, while T4 supports maximum speeds within cables up to 2m long). It also supports convenient functions such as wake-up of sleep mode and direct DMA (Direct Memory Access). 

The T3 system only needed to support 16Gbps for the PCIe connection, which was the maximum speed achievable for an external SSD device. For Thunderbolt 4 certification, the PCIe bandwidth must be doubled to 32 Gbps. 

With Thunderbolt 3, you can connect multiple Thunderbolt devices in a long chain, but removing any one of them (except the last one in the chain) makes all other devices unusable. 

Thunderbolt 4 offers a feature called Hubbing that allows you to use up to four Thunderbolt ports on a hub or dock. Each port is a separate 'branch' that can be separated without affecting other Thunderbolt devices connected to the other port.

What is USB4?

USB4 (which makes no difference between USB 4 and USB 4 in that it may be a futile attempt to prevent it from becoming USB 4.1) is based on the Thunderbolt 3 protocol specification and supports throughputs up to 40 Gbps. 

USB4 looks exactly like USB-C and USB 3.2, Thunderbolt 3 and 4. The minimum specification is 20Gbps, 1 4K display, 7.5W power supply, but it can handle up to 40Gbps and 2 displays, 100W power supply. 

But of course, there are variations. The bandwidth of USB4 Gen 2x2 is 20Gbps. USB4 Gen 3x2 reaches 40Gbps. It's the fastest USB to date and requires a shorter 0.8m cable like the Thunderbolt 3. 

USB4 is compatible with Thunderbolt 3 and backward compatible with USB 3.2 and USB 2.0. 

It can provide at least 15W of power to the accessory and can support two 4K displays or a single 8K display. 

USB 3.2 allocates a fixed bandwidth to data or video, or provides 100% to video in 'DP Alt mode', while USB4 can dynamically and intelligently allocate bandwidth to video and data according to actual needs.

Getting the right USB-C cable

Whatever the speed of your connection, make sure the cable is at least as fast as specified in the specifications. 

When connecting devices with different USB versions, the data transfer rate is limited by the speed of the slowest connected device. Therefore, a USB 2.0 device or a USB 3.1 device connected to a cable can slow down to the 480Mbps speed of USB 2.0. 

When purchasing a USB-C cable, check the supported charging power and USB data rate. Some cables actually have speed ratings, but not all cables. 

Charging cables that support USB 2.0 can be longer than USB 3.x and USB4 cables, but are limited to 480Mbps data transfer rates and do not support alternate modes. 

Thunderbolt 3 cables with the Thunderbolt logo are backward compatible with all USB-C speeds, but special cables may be required to get the most out of the 10Gbps or 20Gbps USB-C connection. 

Thunderbolt 4 and USB4 cables are compatible and backward compatible. The Thunderbolt 3 cable also works with Thunderbolt 4 and USB4 connections. Thunderbolt 4 cables are compatible with USB 2.0 and all USB-C versions, including 3.0, 3.2, and 4, regardless of cable length. 

If you're buying a USB-C cable, look for USB4 certification for future use, or Thunderbolt 4 to support everything. For longer T4 cables, you need an 'active' cable with an active repeater chipset to boost the signal.