# USB 3.0
**USB 3.0** is the third major version of the Universal Serial Bus (USB) interface standard, released in November 2008 by the USB Implementers Forum (USB-IF) with a 5 Gbps signaling rate branded **SuperSpeed USB**, roughly a tenfold increase over USB 2.0's 480 Mbps.[1](https://www.tomshardware.com/features/usb-decoded-all-the-specs-and-version-numbers) • [2](https://www.ti.com/lit/ml/sszb142b/sszb142b.pdf) The same 5 Gbps capability was later renamed USB 3.1 Gen 1 and then USB 3.2 Gen 1, so a device marked "USB 3.0" and one marked "USB 3.2 Gen 1" operate at the same speed class.[3](https://usb-guide.com/usb-3-0-usb-5gbps-explained-superspeed-usb-full-duplex-data-power-cables-and-real-world-performance/)
| Key fact | Detail |
|---|---|
| Release | November 2008, USB Implementers Forum; branded SuperSpeed USB[1](https://www.tomshardware.com/features/usb-decoded-all-the-specs-and-version-numbers) • [2](https://www.ti.com/lit/ml/sszb142b/sszb142b.pdf) |
| Signaling rate | 5 Gbps per lane, a 10x increase over USB 2.0's 480 Mbps[1](https://www.tomshardware.com/features/usb-decoded-all-the-specs-and-version-numbers) |
| Peak throughput | 500 MB/s after 8b/10b encoding; about 400 MB/s or more realistic to an application once framing and protocol overhead are counted[4](https://www.tomshardware.com/reviews/usb-3-uas-turbo%2C3215-2.html) |
| Bus power | 900 mA at 5 V (4.5 W) from a standard USB 3.0 downstream port, up from 500 mA on USB 2.0[5](https://compliance.usb.org/index.asp?Format=Standard&UpdateFile=Policies) • [6](https://www.totalphase.com/support/articles/200349256-usb-background/) |
| Data path | Full-duplex, using two added shielded differential pairs (SSTX and SSRX) alongside the unchanged USB 2.0 D+/D− pair[6](https://www.totalphase.com/support/articles/200349256-usb-background/) • [7](https://developerhelp.microchip.com/xwiki/bin/view/applications/usb/speeds-specs/superspeed/) |
| Cable limits | 3 m maximum for assemblies without a micro plug, 1 m for assemblies with a micro-USB plug[8](https://compliance.usb.org/index.asp?Format=Standard&UpdateFile=Cables+and+Connectors) |
| Later names | USB 3.1 Gen 1 (2013 renaming), USB 3.2 Gen 1 (2017); consumer-facing name USB 5Gbps[3](https://usb-guide.com/usb-3-0-usb-5gbps-explained-superspeed-usb-full-duplex-data-power-cables-and-real-world-performance/) • [9](https://usbcafe.com/usb-standards/usb-3-0/) |
## Physical layer and full-duplex operation
USB 2.0's differential signaling could not carry 5 Gbps, so USB 3.0 upgraded the physical interface. Cables and connectors add two pairs of differential signals, one for transmit and one for receive, which makes SuperSpeed USB a full-duplex bus in which host and device each act as transmitter and receiver simultaneously.[6](https://www.totalphase.com/support/articles/200349256-usb-background/) The original USB 2.0 lines are unchanged, so USB 2.0 communication can occur in parallel on the same cable, and a USB 3.0 host downgrades to USB 2.0 if it does not detect termination on the receiver side.[6](https://www.totalphase.com/support/articles/200349256-usb-background/)
The Standard-A connector keeps the USB 2.0 form factor but adds five pins: a transmit pair, a receive pair, and a drain ground. Plugs and receptacles are often colored blue to distinguish them from USB 2.0, and a USB 3.0 Standard-A plug fits both USB 2.0 and USB 3.0 receptacles.[6](https://www.totalphase.com/support/articles/200349256-usb-background/) The nine-pin pinout places the SuperSpeed receive pair on pins 5 and 6 and the transmit pair on pins 8 and 9, with a separate GND_DRAIN pin for signal return.[7](https://developerhelp.microchip.com/xwiki/bin/view/applications/usb/speeds-specs/superspeed/) SuperSpeed cables use heavier Shielded Differential Pairs in place of the thin unshielded wiring that sufficed for USB 2.0.[10](https://files.cablewholesale.com/support/technical_articles/usb3_superspeed.php)
## Throughput in practice
The 5 Gbps line rate does not translate directly into file-transfer speed. USB 3.0 uses 8b/10b line coding, which turns eight-bit symbols into ten-bit symbols to keep the signal DC-balanced and allow clock recovery, at a 20 percent bandwidth cost. The 5 Gb/s rate therefore yields 500 MB/s of raw throughput, and the USB 3.0 specification itself states that once link flow control, packet framing, and protocol overhead are considered, 400 MB/s or more delivered to an application is realistic.[4](https://www.tomshardware.com/reviews/usb-3-uas-turbo%2C3215-2.html) Device-side controllers further limit real-world numbers; in Tom's Hardware testing, USB 3.0 storage adapters and enclosures generally stayed below the interface's 500 MB/s peak.[4](https://www.tomshardware.com/reviews/usb-3-uas-turbo%2C3215-2.html)
## Power
USB 3.0 raised the power available to bus-powered devices. An unconfigured device may draw 150 mA (one unit load, up from 100 mA on USB 2.0), and a configured device may draw up to six unit loads, or 900 mA, compared with USB 2.0's 500 mA.[6](https://www.totalphase.com/support/articles/200349256-usb-background/) The USB-IF compliance program states the same limit from the port side: a USB 3.0 peripheral may draw at most 900 mA from a standard USB 3.0 downstream port, while USB 2.0 peripherals attached to such a port remain limited to 500 mA, and a peripheral needing more power must be self-powered.[5](https://compliance.usb.org/index.asp?Format=Standard&UpdateFile=Policies) At 5 V, 900 mA corresponds to 4.5 W.[1](https://www.tomshardware.com/features/usb-decoded-all-the-specs-and-version-numbers)
## Power management
USB 3.0 decouples link power states from device power states and defines four link states, U0 through U3. U0 is the active state in which 5 Gbps packets flow; after idling, link partners enter U1 (standby with fast exit) and then U2 (standby with slower exit), and software can send the link to U3, the suspend state.[11](https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/usb-3-0-lpm-mechanism-) • [6](https://www.totalphase.com/support/articles/200349256-usb-background/) Exit from U1 and U2 takes from microseconds to a few milliseconds, fast enough that links can enter and exit these states even while a device is in use, for example between service intervals of an isochronous endpoint, without the device losing any capabilities.[11](https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/usb-3-0-lpm-mechanism-)
Two protocol changes also cut idle power: USB 3.0 eliminates periodic device polling and no longer broadcasts packets on the bus, so devices can enter low-power states when idle because they no longer have to manage reception of these packets.[6](https://www.totalphase.com/support/articles/200349256-usb-background/) Combining these efficiencies with the lower average transmit power, [Texas Instruments](https://www.edgepedia.org/texas-instruments)' SuperSpeed USB reference material estimates that SuperSpeed USB consumes approximately one-third the power of USB 2.0.[2](https://www.ti.com/lit/ml/sszb142b/sszb142b.pdf)
## Naming history
The version numbers attached to the 5 Gbps rate have changed twice without any change to the underlying capability. When USB 3.1 was introduced in 2013 with a 10 Gbps rate, the original 5 Gbps speed was retroactively renamed USB 3.1 Gen 1, with USB 3.1 Gen 2 referring to the 10 Gbps rate.[1](https://www.tomshardware.com/features/usb-decoded-all-the-specs-and-version-numbers) With USB 3.2 in 2017, the USB-IF folded all prior 3.x specifications into USB 3.2, which identifies three transfer rates: 5 Gbps (USB 3.2 Gen 1), 10 Gbps (USB 3.2 Gen 2), and 20 Gbps (USB 3.2 Gen 2x2, two 10 Gbps lanes).[12](https://usb.org/usb-32-0) For consumer-facing labeling, the USB-IF now recommends speed-based names, "SuperSpeed USB" for 5 Gbps products and, in the newer scheme, USB 5Gbps, rather than specification-generation terminology.[13](https://www.usb.org/sites/default/files/usb_3_2_language_product_and_packaging_guidelines_final.pdf) • [9](https://usbcafe.com/usb-standards/usb-3-0/)
## References
1. [USB Decoded: All the Specs and Version Numbers, Tom's Hardware](https://www.tomshardware.com/features/usb-decoded-all-the-specs-and-version-numbers)
2. [SuperSpeed USB Reference Card (Rev. B), Texas Instruments](https://www.ti.com/lit/ml/sszb142b/sszb142b.pdf)
3. [USB 3.0 / USB 5Gbps Explained, usb-guide.com](https://usb-guide.com/usb-3-0-usb-5gbps-explained-superspeed-usb-full-duplex-data-power-cables-and-real-world-performance/)
4. [Faster USB 3.0 Performance: Examining UASP And Turbo Mode, Tom's Hardware](https://www.tomshardware.com/reviews/usb-3-uas-turbo%2C3215-2.html)
5. [USB-IF Compliance Updates: Policies](https://compliance.usb.org/index.asp?Format=Standard&UpdateFile=Policies)
6. [USB Protocol Overview - USB 2.0 & 3.0, Total Phase](https://www.totalphase.com/support/articles/200349256-usb-background/)
7. [SuperSpeed USB - Developer Help, Microchip](https://developerhelp.microchip.com/xwiki/bin/view/applications/usb/speeds-specs/superspeed/)
8. [USB-IF Compliance Updates: Cables and Connectors](https://compliance.usb.org/index.asp?Format=Standard&UpdateFile=Cables+and+Connectors)
9. [USB 3.0: 5 Gbps Speed, Compatibility, and Naming, USBCafe](https://usbcafe.com/usb-standards/usb-3-0/)
10. [The Speed of the Future: USB 3.0, CableWholesale](https://files.cablewholesale.com/support/technical_articles/usb3_superspeed.php)
11. [USB 3.0 link power management mechanism, Microsoft Learn](https://learn.microsoft.com/en-us/windows-hardware/drivers/usbcon/usb-3-0-lpm-mechanism-)
12. [USB 3.2, USB-IF](https://usb.org/usb-32-0)
13. [USB 3.2 Language, Product and Packaging Guidelines, USB-IF](https://www.usb.org/sites/default/files/usb_3_2_language_product_and_packaging_guidelines_final.pdf)
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*Topic: Encyclopedia › Technology and the built world › Computing and digital systems › Computer hardware › Boards, peripherals & form factors › Peripherals & expansion hardware › External peripheral connectivity and adapters*
*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license