USB 3.2 Doubles Speed Across Existing USB Type-C™ Cables



The USB 3.0 Promoter Group recently announced the USB 3.2 specification, meaning that USB Type-C cables will deliver double the throughput. Now in a final draft review, the new USB 3.2 specification will be released in late September. New devices designed in compliance with USB 3.2 will be theoretically capable of 20 Gbps by enabling multi-lane operation. USB 3.2 can use existing USB Type-C cables that have been certified as SuperSpeed+ (USB 3.1 Gen 2).

Type-C connectors are more universal than USB

If you have two USB 3.2-compliant products using a USB Type-C (USB-C™) cable, throughput can reach either 10 Gbps or 20 Gbps. Here’s why: USB 3.1 Gen 1 cables will double speeds from 5 Gbps to 10 Gbps, and USB 3.1 Gen 2 (SuperSpeed+) cables will double speeds from 10 Gbps to 20 Gbps if both connected products are USB 3.2 compliant. Note that the cable is not what doubles speeds in USB 3.2.

According to a recent USB 3.0 Promoter’s Group press release, “USB Type-C cables were designed to support multi-lane operation to ensure a path for scalable performance. New USB 3.2 hosts and devices can now be designed as multi-lane solutions, allowing for up to two lanes of 5 Gbps or two lanes of 10 Gbps operation…effectively doubling the  performance across existing cables. For example, a USB 3.2 host connected to a USB 3.2 storage device will now be capable of realizing over 2 GB/sec data transfer performance over an existing USB Type-C™ cable that is certified for SuperSpeed USB 10 Gbps.”

Someone to watch is Benson Leung, a Google engineer who has been reviewing USB Type-C cables on Amazon by running full bench tests on them. Says Leung, “The basic premise of USB 3.2 is fairly simple: A Full-Featured USB Type-C cable has 15 wires, 8 of which are SuperSpeed wires. When operating in USB 3.1 Gen 1 or Gen 2 modes, only 4 of those wires are used right now. The other 4 may be assigned to an Alternate Mode like DisplayPort, but when used for USB-only operations, they are dormant. USB 3.2 will double the bandwidth by using all 8 wires for USB in cases where both sides can support it and aren’t using the other 4 wires for an alternate mode.”

Leung has come across dozens of USB Type-C cables on Amazon that advertise as something they are not. He clears the confusion cable-by-cable, as in this Amazon Basics USB 2.0 C-to-C line review: “These are USB 2.0 Type-C cables, meaning that they only support USB 2.0 data, and are not appropriate for consumers looking for a cable to connect their laptop to a Type-C monitor or docking station for video out, or to connect to SuperSpeed USB 3.1 devices such as external HDD or SSDs. However, these should still be good charging cables, though, at up to 60W.”

Figure 1: On this USB Type-C cable, there are only four wires. This was advertised as a SuperSpeed USB 3.1 cable; therefore, it should have four more data wires and an additional ground return wire. (Source: Benson Leung, G+, 2/2016.)

Figure 1: On this USB Type-C cable, there are only four wires. This was advertised as a SuperSpeed USB 3.1 cable; therefore, it should have four more data wires and an additional ground return wire. (Source: Benson Leung, G+, 2/2016.)

Many aren’t aware that USB Type-C connectors are not all automatically operational at USB 3.1 speeds. Type-C connectors are more universal than USB, in that a random black USB Type-C cable in a box o’ cords may support HDMI, Thunderbolt, or anywhere from 480 Mbps (USB 2.0) to the new USB 3.2 speeds. Here’s where certification and trademarked logos on the cables will go a long way to making Type-C cables more user-friendly. The cables may also be marked in small lettering on the sides of the cables or embossed on the plug ends with SS (for 5 Gbps) or SS10 (10 Gbps). If they are not embossed with these markings, then they might support only USB 2.0 (480 Mbps) and charging. Leung has reviewed at least one cable that permanently damaged test equipment, so buyer beware. (Apparently the USB police are not a force to be reckoned with, but we vote with our dollars.)

Some USB history

USB 3.0 (SuperSpeed, 5 Gbps) was released in 2008, but the name was retroactively changed to USB 3.1 Gen 1 a few years later. (Does this qualify as a reason for engineers to beat up marketing?) USB 3.1 Gen 2 (SuperSpeed+) is 10 Gbps. If a USB Type-C cable is rated as USB 3.1 Gen 2, it will support charging, USB 2.0 products, USB 3.1 Gen 2 SuperSpeed (10 Gbps) products, and Alternate Modes (e.g., HDMI, DisplayPort). Note that several products are still labeled as USB 3.0 for 5 Gbps, and USB 3.1 for 10 Gbps, rather than USB 3.1 Gen 1 and USB 3.1 Gen 2, respectively.

Most people don’t realize that USB 3.x, USB Type-C, USB-Alternate Mode, USB-Battery Charging, and USB-PD (Power Delivery) are different specifications. This means that manufacturers can mix and match specs somewhat in a single product. For example, you can buy a USB Type-C-to-Type-C cable that tops out at USB 2.0 speeds. (A USB 2.0-only USB Type-C cable is possible, and would only have four wires, which you can test with a multimeter. The cable would have four wires like the one in Figure 1.) On the other end of the spectrum, if you want USB 3.2 data rates at 20 Gbps, you can use an existing USB Type-C cable that is rated for at least 10 Gbps (USB 3.1 Gen 2). Closely examine USB Type-C cables for the USB logo and the SS+ or SS 10 imprint on the connector header if you want top speeds (USB 3.1 Gen 2).

USB 3.0 (SuperSpeed, 5 Gbps) was released in 2008, but the name was retroactively changed to USB 3.1 Gen 1 a few years later. (Does this qualify as a reason for engineers to beat up marketing?) USB 3.1 Gen 2 (SuperSpeed+) is 10 Gbps. If a USB Type-C cable is rated as USB 3.1 Gen 2, it will support charging, USB 2.0 products, USB 3.1 Gen 2 SuperSpeed (10 Gbps) products, and Alternate Modes (e.g., HDMI, DisplayPort). Note that several products are still labeled as USB 3.0 for 5 Gbps, and USB 3.1 for 10 Gbps, rather than USB 3.1 Gen 1 and USB 3.1 Gen 2, respectively.

Most people don’t realize that USB 3.x, USB Type-C, USB-Alternate Mode, USB-Battery Charging, and USB-PD (Power Delivery) are different specifications. This means that manufacturers can mix and match specs somewhat in a single product. For example, you can buy a USB Type-C-to-Type-C cable that tops out at USB 2.0 speeds. (A USB 2.0-only USB Type-C cable is possible, and would only have four wires, which you can test with a multimeter. The cable would have four wires like the one in Figure 1.) On the other end of the spectrum, if you want USB 3.2 data rates at 20 Gbps, you can use an existing USB Type-C cable that is rated for at least 10 Gbps (USB 3.1 Gen 2). Closely examine USB Type-C cables for the USB logo and the SS+ or SS 10 imprint on the connector header if you want top speeds (USB 3.1 Gen 2).

There’s another specification that does not automatically get conferred on USB Type-C cables, and that’s the USB-PD specification, which is about delivering power of up to 100W. (The highest power level uses 20V at 5A to deliver 100W.) Again, this does not mean that all Type-C cables can charge at all five power levels described in USB-PD. (There’s a battery charging spec, as well.) This could get very misleading to consumers. Imagine working your way through the aisles at Fry’s or Best Buy and you cannot find adequate information on the packaging to determine if you have a cable that will do it all. Alternate mode allows a USB Type-C cable to be re-purposed for VESA DisplayPort, HDMI, MHL, and Thunderbolt. More serial protocols may become available for use on the full-featured USB Type-C cable.

A cable that does it all?

What kind of cable has it all? A USB 3.1 Gen 2, full-featured USB Type-C cable should have 10 more wires than your standard USB 2.0 Type-C to USB 2.0 Type-C cable. The extra wires exist so the cable can be re-purposed for Alternate Mode. You will be able to use the same full-featured USB Type-C cable for HDMI and USB 3.1 SuperSpeed, for example. The USB Type-C connector has 24 pins. The USB Type-C connector looks the same in every case, but to achieve USB 3.1 Gen 1 (SuperSpeed), USB 3.1 Gen 2 (SuperSpeed Plus), or Alternate Mode, the extra wires must be connected and a transceiver (PHY) that supports the additional technologies must be present. Any USB Type-C cable with 24 wires should be able to support Alternate Mode.

Figure 2: USB Type-C configured as a Thunderbolt Cable. (Source: Cypress Semiconductor).

Figure 2: USB Type-C configured as a Thunderbolt Cable. (Source: Cypress Semiconductor).

Although it’s confusing, it’s ungrateful to whine, since it’s a spectacular technology and beats having multiple charging standards (and separate cords) for every device. More than one of us has a huge tangle of black cords for various laptops, old tablets, phones, miscellaneous small appliances, and adapters. (Why must they all be black?) USB cables are confusing for the consumer since you almost have to test a cable to determine if the package is saying what you think it is saying. Not everyone is following the rules and making it crystal clear as to what their USB Type-C cable can do.

Digging through a box of black cords will quickly get frustrating. Hint: By specification, the USB 3.1 Gen 2 (10 Gbps) cables are limited to < 1 meter in length, although you can still have a short USB 2.0-only Type-C to Type-C cable. It’s possible for a USB Type-C cable that’s longer than one meter to deliver a 100W output as long as it’s configured to support USB-PD in the first place.

If the USB Type-C cable packaging does not clearly state what you are looking for, then don’t buy it. To double the speeds (per USB 3.2), the USB products connected to the Type-C USB 3.1 cable are on the hook to make full use of a full-featured USB Type-C cable and deliver double the speeds (10 or 20 Gbps). Look for cables from reputable manufacturers and sellers, read reviews, or make sure there’s a good return policy in place.

Oh, and invest in a good label-making machine for those cords. Your future self will thank you.

Reference for Benson Leung quote can be found at https://www.amazon.com/AmazonBasics-USB-Type-C-2-0-Cable/dp/B01GGKZ1VA

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