USB4
Type | USB | ||
---|---|---|---|
Production history | |||
Designer | USB Promoter Group | ||
Designed | 29 August 2019 | ||
Superseded | USB 3.2 | ||
Daisy chain | No | ||
Audio signal | DisplayPort | ||
Video signal | DisplayPort | ||
Connector | USB-C | ||
Electrical | |||
Max. voltage | 48 V (PD 3.1) | ||
Max. current | 5 A (PD) | ||
Data | |||
Data signal | Yes | ||
Bitrate | 20 Gbit/s (optionally up to 120 Gbit/s) |
Universal Serial Bus 4, marketed as USB4 and sometimes referred to as USB 4.0, is a new technical specification of the Universal Serial Bus data connection standard, released on 29 August 2019 by the USB Implementers Forum.
USB4 allows sharing a single, high-speed data link with multiple devices dynamically. USB4 devices must support 20 Gbit/s data transfer rates and, optionally, the rates of 40 Gbit/s (USB4 version 1.0), 80 Gbit/s (USB4 version 2.0), and 120 Gbit/s.[1][2] In contrast to prior USB protocol standards, USB4 mandates the exclusive use of the USB-C connector and USB Power Delivery specification.[citation needed]
USB4 architecture is based on USB 3.2 specification.[3] It also incorporates elements of the Thunderbolt 3 protocol; however, interoperability with Thunderbolt 3 products is mandatory only on selected USB4 device types.[4]
History[edit]
USB4 was announced in March 2019.[5][6] The USB4 specification version 1.0, released 29 August 2019, uses "Universal Serial Bus 4" and specifically "USB4", that is, the short name branding is deliberate without a separating space, which is different than prior versions. Several news reports before the release of that version use the terminology "USB 4.0" and "USB 4".[7][8] Even after publication of rev. 1.0, some sources write "USB 4", claiming "to reflect the way readers search".[9]
On 1 September 2022, the USB Promoter Group announced the pending release of the USB4 Version 2.0 specification, and the specification was subsequently released on 18 October 2022.[10][11]
At time of publication of version 1.0, promoter companies having employees that participated in the USB4 Specification technical work group were: Apple Inc., Hewlett-Packard, Intel, Microsoft, Renesas Electronics, STMicroelectronics, and Texas Instruments.
Goals stated in the USB4 specification are increasing bandwidth, helping to converge the USB-C connector ecosystem, and "minimize end-user confusion". Some of the key areas to achieve this are using a single USB-C connector type, while retaining compatibility with existing USB and Thunderbolt products.[12]
On 29 April 2020, DisplayPort Alt Mode version 2.0 was released, supporting DisplayPort 2.0 over USB4.[13]
Data transfer modes[edit]
USB4 by itself does not provide any generic data transfer mechanism or device classes like USB 3.x, but serves mostly as a way to tunnel other protocols like USB 3.2, DisplayPort, and optionally PCIe. While it does provide a native Host-to-Host protocol, as the name implies it is only available between two connected hosts; it is used to implement Host IP Networking. With the USB4 1.0 specification, when the host and device do not support optional PCIe tunneling, the non-display bandwidth is limited to mandatory USB 3.2 10 Gbit/s, with optional[disputed ] support for USB 3.2 20 Gbit/s. The USB4 2.0 specification named this USB3 Gen X tunneling and introduced optional support for a new USB3 Gen T tunneling that extends the USB3 protocol to be able to use the maximum available bandwidth.
USB4 V2.0 specifies tunneling of:
USB4 also includes support of a DisplayPort alternate mode. That means, DisplayPort signalling (including audio/video signals) can be sent either via USB4 tunneling or using a USB-C alternate mode. DisplayPort 2.1 specification supports a video resolution up to 8K at 60 Hz with HDR10 color depth, and data rate up to 80 Gbit/s which is the same amount available to USB data, but just unidirectional.[14]
Legacy USB (1–2) is always supported using the dedicated wires in the USB-C connector.
Some transfer modes are supported by all USB4 devices, support for others is optional. The requirements for supported modes depend on the type of device.
Mode | Host | Hub | Peripheral device |
---|---|---|---|
Legacy USB (1–2) (max. 480 Mbit/s) | Yes | Yes | Yes |
USB4 Gen 2 (10 or 20 Gbit/s) | Yes | Yes | Yes |
USB4 Gen 3 (20 or 40 Gbit/s) | Optional | Yes | Optional |
USB4 Gen 4 (80 or 120 Gbit/s) | Optional | Optional | Optional |
Tunneled USB 3.2 Gen 2×1 (10 Gbit/s) | Yes | Yes | Optional |
Tunneled USB 3.2 Gen 2×2 (20 Gbit/s) | Optional | Optional | Optional |
Tunneled USB3 Gen T (10–80 Gbit/s) | Optional | Optional | Optional |
Tunneled DisplayPort | Yes | Yes | Optional |
Tunneled PCI Express | Optional | Yes | Optional |
Host-to-Host communications | Yes | Yes | — |
USB-C DisplayPort Alternate Mode | Yes | Yes | Optional |
USB-C Thunderbolt Alternate Mode | Optional | Yes | Optional |
Other USB-C Alternate Modes | Optional | Optional | Optional |
Mode Name | Old Name(s) | Encoding | Multiple Lanes | Lane Rate (Gbit/s) |
Nominal Rate | USB-IF Marketing Name[16][17] | Logo | |
---|---|---|---|---|---|---|---|---|
(Gbit/s) | (GB/s) | |||||||
USB 2.0 (High-Speed) | NRZI w/ bit stuffing | Single | 0.480 | 0.480 | 0.060 | Hi-Speed USB | ||
USB 3.2 Gen 1×1 | USB 3.0 (SuperSpeed), USB 3.1 Gen 1 |
8b/10b | Single | 5 | 5 | 0.625 | USB 5Gbps | |
USB 3.2 Gen 1×2 | Dual | 5 | 10 | 1.2 | — | |||
USB 3.2 Gen 2×1[a] | USB 3.1 Gen 2 | 128b/132b | Single | 10 | 10 | 1.2 | USB 10Gbps | |
USB 3.2 Gen 2×2[a] | Dual | 10 | 20 | 2.4 | USB 20Gbps[18] | |||
USB4 Gen 2×1[a] | 64b/66b[b] | Single | 10 | 10 | 1.2 | — | ||
USB4 Gen 2×2[a] | Dual | 10 | 20 | 2.4 | USB 20Gbps | |||
USB4 Gen 3×1 | 128b/132b[b] | Single | 20 | 20 | 2.4 | — | ||
USB4 Gen 3×2 | Dual | 20 | 40 | 4.8 | USB 40Gbps | |||
USB4 Gen 4[c] | PAM-3[19] | Symmetric | 40 | 80 | 9.6 | USB 80Gbps | ||
Asymmetric | 40 | 120 | 14.4 | — |
- ^ a b c d USB4 Gen 2×1 and Gen 2×2 is different from USB 3.2 Gen 2×1 and Gen 2×2 respectifely. They only signify the same speed, but are coded differently on the electrical layer.
- ^ a b USB4 can use optional Reed–Solomon forward error correction (RS FEC). In this mode, 12 × 16 B (128 bit) symbols are assembled together with 2 B (12 bit + 4 bit reserved) synchronisation bits indicating the respective symbol types and 4 B of RS FEC to allow to correct up to 1 B of errors anywhere in the total 198 B block.
- ^ Gen 4 always has dual lanes.
Although USB4 is required to support dual-lane modes, it uses single-lane operations during initialization of a dual-lane link; single-lane link can also be used as a fallback mode in case of a lane bonding error.
In Thunderbolt compatibility mode, the lanes are driven slightly faster at 10.3125 Gbit/s (for Gen 2) and 20.625 Gbit/s (for Gen 3), as required by Thunderbolt specifications (these are called legacy speeds and rounded speeds[20]). After removal of 64b/66b encoding, those also become round, 20.625/66*64 = 20.000 Gbit/s.
Cable Length Limitations[edit]
Cables are sold at 16.5ft for USB 3.2, and 6.6ft for USB4 but there are no reliable sources to support these speeds functioning at specification.
USB Specification | Max. Data Transfer Rate | Recommended Cable Length |
---|---|---|
USB 1.0 (Full Speed) | 12 Mb/s | 3 m (9 ft.) |
USB 2.0 (High Speed) | 480 Mb/s | 5 m (16 ft.) |
USB 3.2 Gen 1 | 5 Gb/s | 2-3 m (6-9 ft.) |
USB 3.2 Gen 2 | 10 Gb/s | 3 m (9 ft.) |
USB 3.2 Gen 2x2 (USB-C only) | 20 Gb/s | 3 m (9 ft.) |
USB4 (USB-C only) | 40 Gb/s | 0.8 m (31 ins) |
Power delivery[edit]
USB4 requires USB Power Delivery (USB PD). A USB4 connection needs to negotiate a USB PD contract before being established. A USB4 source must at least provide 7.5 W (5 V, 1.5 A) per port. A USB4 sink must require less than 250 mA (default), 1.5 A, or 3 A @ 5 V of power (depending on USB-C resistor configuration) before USB PD negotiation. With USB PD, up to 240 W of power is possible with 'Extended power range' (5 A at 48 V). For 'Standard Power range' up to 100 W is possible (5 A at 20 V).
Thunderbolt 3 compatibility[edit]
The USB4 specification states that a design goal is to "Retain compatibility with existing ecosystem of USB and Thunderbolt products." Compatibility with Thunderbolt 3 is required for USB4 hubs; it is optional for USB4 hosts and USB4 peripheral devices.[22] Compatible products need to implement 40 Gbit/s mode, at least 15 W of supplied power, and the different clock; implementers need to sign the license agreement and register a Vendor ID with Intel.[23]
Pinout[edit]
USB4 has 24 pins in a symmetrical USB type C shell. USB4 has 12 A pins on the top and 12 B pins on the bottom.[24]
USB4 has two lanes of differential SuperSpeed pairs. Lane one uses TX1+, TX1−, RX1+, RX1− and lane two uses TX2+, TX2−, RX2+, RX2−. USB4 transfers data at 20 Gbit/s per lane. USB4 also keeps the differential D+ and D− for USB 2.0 transfer.[25]
The CC configuration channels have the roles of creating a relationship between attached ports, detecting plug orientation due to the reversible USB type C shell, discovering the VBUS power supply pins, determining the lane ordering of the SuperSpeed lanes, and finally the USB protocol makes the CC configuration channel responsible for entering USB4 operation.[26]
Pin | Name | Description |
---|---|---|
A1 | GND | Ground return |
A2 | SSTXp1 ("TX1+") | SuperSpeed differential pair #1, TX, positive |
A3 | SSTXn1 ("TX1-") | SuperSpeed differential pair #1, TX, negative |
A4 | VBUS | Bus power |
A5 | CC1 | Configuration channel |
A6 | Dp1 | USB 2.0 differential pair, position 1, positive |
A7 | Dn1 | USB 2.0 differential pair, position 1, negative |
A8 | SBU1 | Sideband use (SBU) |
A9 | VBUS | Bus power |
A10 | SSRXn2 ("RX2-") | SuperSpeed differential pair #4, RX, negative |
A11 | SSRXp2 ("RX2+") | SuperSpeed differential pair #4, RX, positive |
A12 | GND | Ground return |
Pin | Name | Description |
---|---|---|
B12 | GND | Ground return |
B11 | SSRXp1 | SuperSpeed differential pair #2, RX, positive |
B10 | SSRXn1 | SuperSpeed differential pair #2, RX, negative |
B9 | VBUS | Bus power |
B8 | SBU2 | Sideband use (SBU) |
B7 | Dn2 | USB 2.0 differential pair, position 2, negative[a] |
B6 | Dp2 | USB 2.0 differential pair, position 2, positive[a] |
B5 | CC2 | Configuration channel |
B4 | VBUS | Bus power |
B3 | SSTXn2 | SuperSpeed differential pair #3, TX, negative |
B2 | SSTXp2 | SuperSpeed differential pair #3, TX, positive |
B1 | GND | Ground return |
Software support[edit]
USB4 is supported by:
- Linux kernel 5.6, released on 29 March 2020[27]
- macOS Big Sur (11.0), released on 12 November 2020[28]
- Windows 11, released on 5 October 2021[29]
Hardware support[edit]
During CES 2020, USB-IF and Intel stated their intention to allow USB4 products that support all the optional functionality as Thunderbolt 4 products. The first products compatible with USB4 were Intel's Tiger Lake processors, with more devices appearing around the end of 2020.[30][31]
Brad Saunders, CEO of the USB Promoter Group, anticipates that most PCs with USB4 will support Thunderbolt 3, but for phones the manufacturers are less likely to implement Thunderbolt 3 support.[9]
On 3 March 2020, Cypress Semiconductor announced new Type-C power (PD) controllers supporting USB4, CCG6DF as dual port and CCG6SF as single-port.[32]
In November 2020, Apple unveiled MacBook Air (M1, 2020), MacBook Pro (13-inch, M1, 2020), and Mac mini (M1, 2020) featuring two USB4 ports.
AMD also stated that Zen 3+ (Rembrandt) processors will support USB4[33] and released products do have this feature after a chipset driver update.[34] However, AMD has only announced support for USB 3.2 Gen 2×2 in Zen 4 processors that were released in September 2022.[35][36] Intel supports Thunderbolt 3 and USB-C with the mobile 9th generation processors in 2019.
References[edit]
- ^ "USB4® Specification v2.0". USB-IF. October 2022.
- ^ "USB-IF Announces Publication of New USB4® Specification to Enable USB 80Gbps Performance" (PDF). 2022-10-18.
- ^ USB4® Specification v2.0
2 Architectural Overview
Enhanced SuperSpeed USB, as defined in the USB 3.2 Specification, remains the fundamental architecture for USB data transfer on a USB4 Fabric. - ^ see 2.1.5 (page 15) in https://www.usb.org/sites/default/files/USB4%20Specification.zip
- ^ Hill, Brandon (2019-03-04). "USB4 Leverages Thunderbolt 3 Protocol Doubling Speeds To 40Gbps". HotHardware. Archived from the original on 2021-10-23. Retrieved 2020-04-28.
- ^ "USB4 announced with 40Gbps bandwidth, it's based on Thunderbolt 3". GSMArena.com. Archived from the original on 2022-01-15. Retrieved 2020-04-29.
- ^ "With USB 4, Thunderbolt and USB will converge". 2019-03-04. Archived from the original on 2022-09-10. Retrieved 2020-05-01.
- ^ Hagedoorn, Hilbert. "USB 4.0 Will Arrive in Late 2020". Guru3D. Archived from the original on 2021-10-26. Retrieved 2020-04-30.
- ^ a b September 2019, Avram Piltch 03 (2021-04-20). "USB 4: Everything We Know So Far". Tom's Hardware. Archived from the original on 2021-06-30. Retrieved 2020-04-30.
{{cite web}}
: CS1 maint: numeric names: authors list (link) - ^ "USB Promoter Group Announces USB4 Version 2.0". www.businesswire.com. 2022-09-01. Archived from the original on 2022-09-02. Retrieved 2022-09-02.
- ^ "USB-IF Announces Publication of New USB4® Specification to Enable USB 80Gbps Performance" (PDF). USB-IF. USB Implementers Forum. 2022-10-18. Retrieved 2023-01-19.
- ^ USB4 Spec. p.1
- ^ Association (VESA), Video Electronics Standards. "VESA Releases Updated DisplayPort Alt Mode Spec to Bring DisplayPort 2.0 Performance to USB4 and New USB Type-C Devices". www.prnewswire.com. Archived from the original on 2021-11-24. Retrieved 2020-04-30.
- ^ "VESA RELEASES UPDATED DISPLAYPORT ALT MODE SPEC TO BRING DISPLAYPORT 2.0 PERFORMANCE TO USB4 AND NEW USB TYPE-C DEVICES". Vesa. 2020-04-29. Archived from the original on 2021-11-23. Retrieved 2021-08-09.
- ^ "USB Promoter Group USB4 Specification v2.0". USB Implementers Forum. 2019-08-29. Archived from the original on 2023-03-26. Retrieved 2023-05-11.
- ^ "USB 3.2 Specification Language Usage Guidelines from USB-IF" (PDF). Archived (PDF) from the original on 2021-11-03. Retrieved 2021-11-13.
- ^ "USB Performance Logo Usage Guidelines" (PDF). Archived (PDF) from the original on 2023-03-23. Retrieved 2023-05-11.
- ^ https://www.usb.org/sites/default/files/usb_data_performance_language_usage_guidelines_jan_2024.pdf
- ^ GraniteRiverLabs, Team (2023-01-17). "Welcome to the 80Gpbs Ultra-High Speed Era of USB4 | GraniteRiverLabs Taiwan". www.graniteriverlabs.com. Archived from the original on 2023-02-21. Retrieved 2023-02-21.
- ^ "How to Test and Troubleshoot USB4" (PDF). Archived (PDF) from the original on 2022-09-10. Retrieved 2022-07-25.
- ^ "How to Beat the Maximum USB Cable Length Limit". blog.tripplite.com. Retrieved 2024-03-14.
- ^ USB4 Specification V1.0 August 2019 Chapter 13: "A USB4 host and USB4 peripheral device may optionally support TBT3-Compatibility. If a USB4 host or USB4 peripheral device supports TBT3-Compatibility, it shall do so as defined in this chapter".
- ^ "USB4 Thunderbolt3 Compatibility Requirements Specification – USB-F". Archived from the original on 2021-11-24. Retrieved 2021-11-13.
- ^ "The Relationship Between USB4 and the USB Type-C Connector". Total Phase Blog. 2020-02-18. Archived from the original on 2022-09-10. Retrieved 2022-04-05.
- ^ "USB4 Specification". www.usb.org. Archived from the original on 2022-04-14. Retrieved 2022-04-05.
- ^ Leung, Benson (2018-11-19). "USB Type-C™'s Configuration Channel". Medium. Archived from the original on 2022-04-05. Retrieved 2022-04-05.
- ^ "Linux 5.6 Kernel Released With WireGuard, USB4, New AMD + Intel Hardware Support – Phoronix". Phoronix.com. Archived from the original on 2021-11-02. Retrieved 2020-04-28.
- ^ "Introducing the next generation of Mac". apple.com. 2020-11-10. Archived from the original on 2021-03-01. Retrieved 2020-11-13.
- ^ windows-driver-content. "Introduction to the USB4 connection manager in Windows". docs.microsoft.com. Archived from the original on 2021-11-03. Retrieved 2021-11-03.
- ^ "USB4 devices are clear to roll out next year". Engadget. Archived from the original on 2021-11-24. Retrieved 2020-04-28.
- ^ Maislinger, Florian (2019-06-14). "First USB 4 devices to be launched at the end of 2020". Archived from the original on 2021-11-24. Retrieved 2020-04-28.
- ^ Shilov, Anton. "Cypress Announces USB 3.2 & USB4-Ready Controllers: EZ-PD CCG6DF & CCG6SF". www.anandtech.com. Archived from the original on 2021-12-06. Retrieved 2020-04-28.
- ^ Cutress, Ian (2022-01-04). "AMD Announces Ryzen 6000 Mobile CPUs for Laptops: Zen3+ on 6nm with RDNA2 Graphics". Anandtech. Archived from the original on 2022-06-25. Retrieved 2022-07-26.
- ^ Klotz, Aaron (2022-06-28). "AMD Introduces USB 4 Support in Chipset Update for Ryzen 6000 Mobile (Updated)". Tom's Hardware.
- ^ Bonshor, Gavin (2022-05-23). "AMD Ryzen 7000 Announced: 16 Cores of Zen 4, Plus PCIe 5 and DDR5 for Socket AM5, Coming This Fall". Anandtech. Archived from the original on 2022-07-26. Retrieved 2022-07-26.
- ^ "AMD confirms Zen4 & Ryzen 7000 series lineup: Raphael in 2022, Dragon Range and Phoenix in 2023". VideoCardz.com. Retrieved 2022-11-29.
External links[edit]
- USB4 | USB-IF
- USB4 | USB-IF
- USB4 specifications can be downloaded from usb.org:
- USB4 Specification | USB-IF 2019-08-29
- USB4 Adopters Agreement | USB-IF 2019-08-29
- Podcast with Jit Lim from Keysight, 2019-11-21