Thunderbolt (interface)
Thunderbolt is the brand name of a hardware interface for the connection of external peripherals to a computer. It was developed by Intel in collaboration with Apple. It was initially marketed under the name Light Peak, and first sold as part of an end-user product on 24 February 2011.
Thunderbolt combines PCI Express and DisplayPort into two serial signals and provides DC power via a single cable. Up to six peripherals may be supported by a single connector through various topologies. Thunderbolt 1 and 2 use the same connector as Mini DisplayPort, whereas Thunderbolt 3, 4, and 5 use the USB-C connector and support USB devices.
Description
Thunderbolt controllers multiplex one or more individual data lanes from connected PCIe and DisplayPort devices for transmission via two duplex Thunderbolt lanes, then de-multiplex them for use by PCIe and DisplayPort devices on the other end. A single Thunderbolt port supports up to six Thunderbolt devices via hubs or daisy chains; as many of these as the host has DP sources may be Thunderbolt monitors. A device with fewer than four PCIe lanes still qualifies as a Thunderbolt device, but will not support the full capabilities and speeds of Thunderbolt.A single Mini DisplayPort monitor or other device of any kind may be connected directly or at the very end of the chain. Thunderbolt is interoperable with DP-1.1a compatible devices. When connected to a DP-compatible device, the Thunderbolt port can provide a native DisplayPort signal with four lanes of output data at no more than 5.4 Gbit/s per Thunderbolt lane. When connected to a Thunderbolt device, the per-lane data rate achieves 10 Gbit/s and the four Thunderbolt lanes are configured as two duplex lanes, each 10 Gbit/s, comprising one lane of input and one lane of output.
Thunderbolt can be implemented on PCIe graphics cards, which have access to DisplayPort data and PCIe connectivity, or on the motherboard of computers with onboard video, such as the MacBook Air.
The interface was originally intended to run exclusively on an optical physical layer using components and flexible optical fiber cabling developed by Intel partners and at Intel's Silicon Photonics lab. It was initially marketed under the name Light Peak and, after 2011, as Silicon Photonics Link. However, it was eventually discovered that conventional copper wiring could furnish the desired 10 Gbit/s per channel at lower cost.
This copper-based version of the Light Peak concept was co-developed by Apple and Intel. Apple registered Thunderbolt as a trademark, but later transferred the mark to Intel, which held overriding intellectual property rights. Thunderbolt was commercially introduced on Apple's 2011 MacBook Pro, using the same Apple-developed connector as Mini DisplayPort.
In January 2013, Sumitomo Electric Industries began selling optical Thunderbolt cables of up to in length in Japan, while in late September 2013, Corning Inc. started selling fiber-optic cables of up to in length in the United States.
History
(2009)
introduced Light Peak at the 2009 Intel Developer Forum, using a prototype Mac Pro logic board to run two 1080p video streams plus LAN and storage devices over a single 30-meter optical cable with modified USB ends. The system was driven by a prototype PCI Express card, with two optical buses powering four ports. Jason Ziller, head of Intel's Optical I/O Program Office, presented the internal components of the technology under a microscope and the delivery of data through an oscilloscope. The technology was described as having an initial speed of 10 Gbit/s over plastic optical cables, alongside promising a final speed of 100 Gbit/s. At the show, Intel announced Light Peak-equipped systems would begin to appear in 2010, and posted a YouTube video showing Light Peak-connected HD cameras, laptops, docking stations, and HD monitors.On 4 May 2010, in Brussels, Intel demonstrated a laptop with a Light Peak connector, indicating that the technology had shrunk enough to fit inside such a device, and had the laptop send two simultaneous HD video streams down the connection, indicating that at least some fraction of the software/firmware stacks and protocols were functional. At the same demonstration, Intel officials stated they expected hardware manufacturing to begin around the end of 2010.
In September 2010, some early commercial prototypes from manufacturers were demonstrated at the Intel Developer Forum 2010.
(2011)
's Brooke Crothers said it was rumored that the early-2011 MacBook Pro update would include some sort of new data port, and he speculated it would be Light Peak. At the time, there were no details on the physical implementation, and mock-ups appeared showing a system similar to the earlier Intel demos that utilizes a combined USB/Light Peak port. Shortly before the release of the new machines, the USB Implementers Forum announced it would not allow such a combination port, and that USB was not open to modification in that way.Other implementations of the technology began in 2012, with desktop boards offering the interconnection now available.
Apple stated in February 2011 that the port was based on Mini DisplayPort, not USB. As the system was described, Intel's solution to the display connection problem became clear: Thunderbolt controllers multiplex data from existing DP systems with data from the PCIe port into a single cable. Older displays using DP 1.1a or earlier must be located at the end of a Thunderbolt device chain, but native displays can be anywhere along the line. Thunderbolt devices can go anywhere on the chain. In that respect, Thunderbolt shares a relationship with the older ACCESS.bus system, which used the display connector to support a low-speed bus.
Apple states that up to six daisy-chained peripherals are supported per Thunderbolt port and that the display should be attached at the end of the chain if it does not support daisy-chaining.
In February 2011, Apple introduced MacBook Pro, MacBook Pro, and MacBook Pro featuring one Thunderbolt port. In May 2011, Apple introduced the iMac, featuring one Thunderbolt port, and the iMac, featuring two Thunderbolt ports. In July 2011, Apple introduced Mac Mini, MacBook Air, MacBook Air, and Apple Thunderbolt Display, featuring one Thunderbolt port for daisy-chaining or other devices.
In May 2011, Apple announced a new line of iMacs that includes the Thunderbolt interface.
The Thunderbolt port on the new Macs is in the same location relative to other ports and maintains the same physical dimensions and pinout as the prior MDP connector. The main visible difference on Thunderbolt-equipped Macs is a Thunderbolt symbol next to the port.
The DisplayPort standard is partially compatible with Thunderbolt, as the two share Apple's physically compatible MDP connector. The Target Display mode on iMacs requires a Thunderbolt cable to accept a video-in signal from another Thunderbolt-capable computer. A DP monitor must be the last device in a chain of Thunderbolt devices.
Intel announced it would release a developer kit in the second quarter of 2011, while manufacturers of hardware development equipment have indicated they will add support for testing and development of Thunderbolt devices. The developer kit is being provided only on request.
In July 2011, Sony released its Vaio Z21 line of notebook computers that had a "Power Media Dock" that uses optical Thunderbolt to connect to an external graphics card using a combination port that behaves like USB electrically, but that also includes the optical interconnect required for Thunderbolt.
Thunderbolt 1 ran at 10 Gbit/s, making it faster than USB at the time.
(2013)
In June 2013, Intel announced that the next version of Thunderbolt, based on the controller code-named "Falcon Ridge", is officially named "Thunderbolt 2" and entered production in 2013. The data rate of 20 Gbit/s is made possible by joining the two existing 10 Gbit/s-channels, which does not change the maximum bandwidth, but makes its usage more flexible.In June 2013, Apple announced the Mac Pro featuring six Thunderbolt 2 ports. In October 2013, Apple announced MacBook Pro, and MacBook Pro featuring two Thunderbolt 2 ports. In October 2014, Apple announced Mac Mini, and iMac featuring two Thunderbolt 2 ports. In March 2015, Apple announced MacBook Air, and MacBook Air featuring one Thunderbolt 2 port.
At the physical level, the bandwidth of Thunderbolt 1 is identical to that of Thunderbolt 2, which means Thunderbolt 1 cabling is compatible with Thunderbolt 2 interfaces. At the logical level, Thunderbolt 2 enables channel aggregation, whereby the two previously separate 10 Gbit/s channels can be combined into a single logical 20 Gbit/s channel.
Intel says Thunderbolt 2 will be able to transfer a 4K video while simultaneously displaying it on a discrete monitor.
Thunderbolt 2 incorporates DisplayPort 1.2 support, which allows for video streaming to a single 4K video monitor or dual QHD monitors. Thunderbolt 2 is backward compatible, which means that all Thunderbolt cables and connectors are compatible with Thunderbolt 1.
The first Thunderbolt 2 product for the consumer market was Asus's Z87-Deluxe/Quad motherboard, announced on 19 August 2013, and the first system released with Thunderbolt 2 was Apple's late 2013 Retina MacBook Pro, on 22 October 2013.
(2015)
Thunderbolt 3 is a hardware interface developed by Intel. It shares USB-C connectors with USB, supports USB 3.1 Gen 2, and can require special active cables for maximum performance for cable lengths over 0.5 meters. Compared to Thunderbolt 2, it doubles the bandwidth to 40 Gbit/s. It allows up to four lanes of PCI Express 3.0 for general-purpose data transfer, and four lanes of DisplayPort 1.4 HBR3 for video, but the maximum combined data rate cannot exceed 40Gbit/s; video data is prioritized and so uses all needed bandwidth, the remainder being available to PCIe. DP 1.2 support is mandatory, while DP 1.4 is optional. Other overheads are possible on PCIe data and Thunderbolt 3 protocol, the last one gives only 21.6 Gbit/s to 25 Gbit/s. Thunderbolt 3 uses 64b/66b encoding after that, which means the real rate is bigger than 40 Gbit/s, 2 times 20.625 Gbit/s.Intel's Thunderbolt 3 controller halves power consumption, and simultaneously drives two external 4K displays at 60 Hz instead of just the single display previous controllers can drive. The new controller supports PCIe 3.0 and other protocols, including DisplayPort 1.2. Thunderbolt 3 has up to 15 watts of power delivery on copper cables and no power delivery capability on optical cables. Using USB-C on copper cables, it can incorporate USB power delivery, allowing the ports to source or sink up to 100 watts of power. This eliminates the need for a separate power supply from some devices. Thunderbolt 3 allows backwards compatibility with the first two versions by the use of adapters or transitional cables.
Intel offers three varieties for each of the controllers:
- Double Port uses a PCIe 3.0 ×4 link to provide two Thunderbolt 3 ports
- Single Port uses a PCIe 3.0 ×4 link to provide one Thunderbolt 3 port
- Low Power uses a PCIe 3.0 ×2 link to provide one Thunderbolt 3 port.
Support was added to Intel's Skylake architecture chipsets, shipping during late 2015 into early 2016.
Devices with Thunderbolt 3 ports began shipping at the beginning of December 2015, including notebooks running Microsoft Windows, as well as motherboards, and a 0.5 m Thunderbolt 3 passive USB-C cable.
In October 2016, Apple announced MacBook Pro, which, as the name indicates, features two Thunderbolt 3 ports, MacBook Pro, and MacBook Pro, which features four Thunderbolt 3 ports. In June 2017, Apple announced iMac, iMac, iMac which feature two Thunderbolt 3 ports, as well as the iMac Pro, which featured four Thunderbolt 3 ports and was released in December 2017. In October 2018, Apple announced MacBook Air, featuring 2 Thunderbolt 3 ports and Mac mini featuring four Thunderbolt 3 ports. In June 2019, Apple unveiled Mac Pro and Mac Pro featuring up to twelve Thunderbolt 3 ports, and Pro Display XDR, which features one Thunderbolt 3 port, both released in December 2019. In March 2022, Apple released Studio Display featuring one Thunderbolt 3 port.
On 8 January 2018, Intel announced a product refresh with "enhanced robustness" and support for DisplayPort 1.4. Intel offers a single-port and double-port version of this host controller and a peripheral controller supporting two Thunderbolt 3 ports. The new peripheral controller can now act as a USB sink.
The Apple Pro Display XDR, which macOS allows to connect using two HBR3 connections to a Mac, doesn't support Display Stream Compression. That would be 51.84 Gbit/s, impossible for Thunderbolt 3, but it works because the two 3008×3384 10bpc 60 Hz 648.91 MHz signals of the XDR display only require 38.9 Gbit/s total, and Thunderbolt does not transmit the DisplayPort stuffing symbols used to fill the HBR3 bandwidth.