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Thunderbolt (interface)

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Thunderbolt
File:Thunderbolt logo.svg
Type Dual-protocol I/O[1]
Production history
Designer Intel[2]
Designed 2009
Manufacturer Various
Produced February 2011–present
General specifications
Length 3 meters maximum (copper)[3]
Width 8.3 mm
Height 5.4 mm
Hot pluggable Yes
Daisy chain Yes, up to 6 devices[3]
External Yes
Connector Mini DisplayPort
Electrical
Signal 10 W[3]
Data
Data signal Yes
Bitrate 10 Gbit/s PCIe bi-directional
10 Gbit/s DisplayPort
100 Gbit/s (over next decade)[4]
Protocol PCI Express, DisplayPort v1.1a[3]

Thunderbolt (originally codenamed Light Peak) is an interface for connecting peripheral devices to a computer via an expansion bus. Thunderbolt was developed by Intel and brought to market with technical collaboration from Apple Inc. It was introduced commercially on Apple's updated MacBook Pro lineup on February 24, 2011, using the same port and connector as Mini DisplayPort.

Thunderbolt essentially combines PCI Express and DisplayPort into a new serial data interface that can be carried over longer and less costly cables. Because PCI Express is widely supported by device vendors and built into most of Intel's modern chipsets, Thunderbolt can be added to existing products with relative ease. Thunderbolt driver chips fold the data from these two sources together, and split them back apart again for consumption within the devices. This makes the system backward compatible with existing DisplayPort hardware upstream of the driver.

Apple's iMac 2011 showed that this compatibility is limited to the video output, as video input is incompatible with DisplayPort and mini-DisplayPort devices, and only allow Thunderbolt-equipped computers to send a video signal to 2011 iMac's through Thunderbolt cables, exclusively, breaking compatibility with existing DisplayPort and mini-DisplayPort equipped computers.

The interface was originally designed to use flexible optical fiber cables, but a version using conventional copper wiring was also developed to furnish the desired 10 Gb/s bandwidth at lower cost. Intel's implementation of the port adapter folds Thunderbolt and DisplayPort data together, allowing both to be carried over the same cable at the same time. A single Thunderbolt port supports hubs as well as a daisy chain of up to seven Thunderbolt devices; up to two of these devices may be high-resolution displays using DisplayPort.[5] Apple sells existing DisplayPort adapters for DVI, dual-link DVI, HDMI, and VGA output from the Thunderbolt port, showing broad compatibility.

History

Introduction

Intel introduced Light Peak at the 2009 Intel Developer Forum (IDF), using a prototype Mac Pro motherboard to run two 1080p video streams plus LAN and storage devices over a single 30-meter optical cable with modified USB ends.[6] The system was driven by a prototype PCI Express card, with two optical buses powering four ports.[7] At the show, Intel claimed that Light Peak-equipped systems would begin to appear in 2010.[8]

On 4 May 2010, in Brussels, Intel demonstrated a laptop with a Light Peak connector, indicating that the technology had shrunk small 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 said they expected hardware manufacturing to begin around the end of 2010.[9]

In September 2010, some early commercial prototypes from manufacturers were demonstrated at Intel Developer Forum 2010.[10]

Copper vs. optical

Originally conceived as an optical technology, Thunderbolt switched to electrical connections to reduce costs and to supply power.[11]

In 2009, Intel officials said the company was "working on bundling the optical fibre with copper wire so Light Peak can be used to power devices plugged into the PC."[12] In 2010, Intel said the original intent was "to have one single connector technology" that would allow "electrical USB 3.0 […] and piggyback on USB 3.0 or 4.0 DC power."[2]

In January 2011, Intel's David Perlmutter told Computerworld that initial Thunderbolt implementations would be based on copper wires.[13] "The copper came out very good, surprisingly better than what we thought," he said.[14]

Intel and industry partners are still developing optical Thunderbolt hardware and cables.[15] The optical fiber cables are to run "tens of meters" but will not supply power, at least not initially.[16][17][18] They are to have two 62.5-micron-wide fibers to transport an infrared signal up to 100 metres (330 ft).[19] The conversion of electrical signal to optical will be embedded into the cable itself, allowing the current display port socket to be future compatible, but eventually Intel hopes for a purely optical transceiver assembly embedded in the PC.[18]

Actual claimed implementation from Intel differs from original claims about "electric cable", to use an "active" cable that embed 1 or 2 communication chip inside the cable to format the signal between Thunderbolt-equipped computers and peripherals. Copper has not been confirmed either.

Market introduction

Macbook Pro Thunderbolt Interface

It was long rumoured that the early-2011 MacBook Pro update would include some sort of new data port, and most of the speculation suggested it would be Light Peak.[20] At the time, there were no details on the physical implementation, and mock-ups appeared showing a system similar to the earlier Intel demos using a combined USB/Light Peak port.[21] Shortly before the release of the new machines, the USB Implementers Forum (USB-IF) announced they would not allow this, stating that USB was not open to modification in this way.

In spite of these comments and speculation, the introduction came as a major surprise when it was revealed that the port was based on DisplayPort, not USB. As the system was described, Intel's solution to the display connection problem became clear: Thunderbolt controllers fold data from existing DisplayPort systems with data from the PCI Express port into a single cable. Older displays, using DisplayPort 1.1 or earlier, have to be located at the end of a Thunderbolt device chain, but newer displays can be placed anywhere along the line.[17] Thunderbolt devices can go anywhere on the chain. In this respect, Thunderbolt shares a relationship with the older ACCESS.bus system, which used the display connector to support a low-speed bus.

Apple actually modified it's page about Thunderbolt Technology [22] to indicate that only 6 peripherals could be linked to a Thunderbolt port, and a Display at the end of the chain.

In late February 2011, Apple introduced its new line of MacBook Pro laptop computers and announced the technology's commercial name would be Thunderbolt, with these machines being the first to feature the new I/O technology. Apple's legacy DisplayPort standard is fully compatible with Thunderbolt, and the two of them share the Mini DisplayPort connector. The Thunderbolt port on the new MacBook Pro laptops is in the same location as and nearly identical in appearance to the Mini DisplayPort port on the previous generations.[5]

mini-DisplayPort devices, and DisplayPort devices (with adapters) are not allowed to send video stream to Thunderbolt-equipped computers, compatibility is restricted to only Thunderbolt-equipped computers when sending video stream to another Thunderbolt-equipped computer, using only Thunderbolt cable.

In May 2011, Apple announced a new line of iMacs that include the Thunderbolt interface.[23]

Intel announced that a developer kit will be released in the second quarter of 2011, [24] while manufacturers of hardware development equipment have indicated they will add support for the testing and development of Thunderbolt devices.[25]

Description

Thunderbolt link connections
Intel will provide 2 types Thunderbolt controllers, 2 port and 1 port. Peripheral side needs the controller, not only PC side.

Thunderbolt is based on the Mini DisplayPort connector developed by Apple. This is electrically identical to "normal" DisplayPort connectors, but uses a smaller connector that is more suitable for use on laptops and other consumer devices. It is expected that Thunderbolt's use of this connector will drive wider acceptance.

Because the PCIe bus does not carry video data, it is unclear whether a standalone PCIe card could offer a Thunderbolt port. The Intel Thunderbolt Technology Brief does not give a conclusive answer.[3] Intel disclosed documentation where video stream is sent to a dual-thunderbolt controller, with the video stream being only sent to one of the thunderbolt Port, giving the assumption that video stream is not mandatory on Thunderbolt implementation.

Thunderbolt can be implemented on graphics cards, which have access to DisplayPort data and PCI express connectivity, or on the motherboard of new devices, such as the MacBook Pro.[5][17][26]

Thunderbolt controllers on the host and peripherals fold the PCIe and DisplayPort data together and unfold them after they exit the cable.[3]

The physical layer of Thunderbolt (in Thunderbolt mode) is very similar to DisplayPort 1.2, with 20 Gbit/s bandwidth. However, Thunderbolt is bi-directional, which often requires sophisticated reflection and cross-talk suppression techniques, such as used in 10 Gigabit Ethernet.

Security

Since Thunderbolt extends the PCI Express bus, which is the main expansion bus in current systems, it allows very low-level access to the system. PCI devices need to have unlimited access to memory, and may thus compromise security.[27] This issue exists with all high-speed expansion buses, including PC Card, ExpressCard and IEEE 1394 interface (FireWire).

It is worth noting that all Intel processors since the introduction of the Nehalem microarchitecture (that is, any CPU branded Core i3, Core i5, Core i7, or later) support VT-d, an IOMMU implementation. This allows the operating system (OS) to isolate a device in its own virtual memory address space (in a manner analogous to the isolation of processes from one another using the MMU). Devices are thus prevented from having access to all of physical memory.

Comparison

PCI

20 Gbit/s Thunderbolt is equivalent to other PCI expansion methods, such as 4 Gbit/s ATI XGP, 5 Gbit/s Shuttle GXT, 2.5 Gbit/s ExpressCard, and 1.066 Gbit/s PCMCIA. These connection methods do not allow for transfer of video signals, but they do allow for connection of a GPU. Such expansion technologies allow for connection of expansion chassis and backplanes such as for usage of extended number of PCI, PCIe, PCI-X, compactPCI, mini-PCI(e) slots. Also, more dedicated solutions may be constructed without using slots. Any conventional PCI devices and drivers can be used, mainly limited by bandwidth requirements. These include common PCI peripherals such as adapters for ISA, USB, (e)SATA, SCSI, serial, parallel, SD, FireWire, Ethernet, Wi-Fi, GPU, video, audio, ExpressCard, PCI expansion boxes and Industrial CompactPCI peripherals. Unlike USB, to redirect PCI to other (virtual) machines, technologies such as I/O virtualization are required.

USB 3.0

USB 3.0 is the latest incarnation of the USB standard, supporting transfer speeds up to 5 Gbit/s. The higher speeds required changes to the cabling. USB 3.0 has backward compatibility with the enormous number of existing USB devices. As of 2009, there are about 2 billion USB devices sold per year, and approximately 6 billion total sold to date.[28]

The USB protocol has historically had a variety of problems when operating at high speeds. The system was host-driven, and relied on messages flowing from the host to keep the data flowing. This introduced high latencies into the system, so high that it seriously affects the maximum throughput. Even at USB 2.0's 480 Mbit/s speeds, throughput only reaches 50% of the maximum, and often much lower.

However, with the advent of USB 3.0, the protocol was revised to add full-duplex signaling and the Bulk Streams communications mode.[29] Streams allow devices to issue asynchronous updates to the host rather than waiting to be polled, tagged to allow devices to accommodate out-of-order operations. This has allowed the creation of protocols such as USB Attached SCSI, which reduce the performance disadvantage USB has previously suffered.

In comparison, Thunderbolt offers twice the peak speed and two independent buses. In theory, a single Thunderbolt port thus has four times the throughput of a USB 3.0 port. In practice, the lower latency even at the end of the chain, and very lightweight PCI Express protocol should offer performance much closer to the theoretical maximums.[17] Intel demonstrated throughputs at 62.5% of the peak using prototype products.[17] Hard drive speed could be the cause of Thunderbolt not getting closer to its theoretical maximum.[30]

DisplayPort v1.2

AMD lamented that Thunderbolt's DisplayPort bandwidth is, in its current incarnation, lower than DisplayPort v1.2's 17 Gbit/s peak video throughput when PCI Express is used as well, if only a single Thunderbolt port is used.[31]

Laptop docking station

The Thunderbolt connection can carry all signals required for a docking station, except charging. The docking station can be constructed independent from the notebook maker if the OS supports the specific devices.[citation needed]

See also

References

  1. ^ "Thunderbolt™ Technology". Intel. Retrieved February 25, 2011.
  2. ^ a b Crothers, Brooke (September 29, 2009). "Sources: 'Light Peak' technology not Apple idea". CNet News. CNet. Retrieved February 23, 2011.
  3. ^ a b c d e f "Technology Brief" (PDF). Intel. Retrieved February 25, 2011.
  4. ^ Lowensohn, Josh (February 24, 2011). "Intel's Thunderbolt: What you need to know (FAQ)". CNet News. CBS Interactive. Retrieved February 25, 2011.
  5. ^ a b c Foresman, Chris (February 24, 2011). "Thunderbolt smokes USB, FireWire with 10 Gb/s throughput". Ars Technica. Condé Nast Digital. Retrieved February 24, 2011.
  6. ^ Patel, Nilay (September 24, 2009). "Video: Intel's Light Peak running an HD display while transferring files... on a hackintosh". Engadget. AOL. Retrieved February 25, 2011.
  7. ^ Jason Ziller (January 26, 2010). Intel Light Peak Interconnect Technology Update (YouTube). Intel. Event occurs at 1:20. Retrieved February 23, 2011.
  8. ^ Shiels, Maggie (September 25, 2009). "Future is TV-shaped, says Intel". BBC News. Retrieved September 27, 2009.
  9. ^ Collins, Barry (May 4, 2010). "Intel shows off first Light Peak laptop". PC Pro. Dennis Publishing. Retrieved May 5, 2010.
  10. ^ Hollister, Sean (September 14, 2010). "Intel's Light Peak optical interconnect shrinks slightly, LaCie, WD, Compal and Avid begin prototyping". Engadget. AOL. Retrieved November 28, 2010.
  11. ^ Hachman, Mark (February 24, 2011). "Intel Thunderbolt Rollout Won't Be Lightning Fast". PC Mag. Ziff Davis. Retrieved February 26, 2011.
  12. ^ Shankland, Stephen (September 23, 2009). "Intel's Light Peak: One PC cable to rule them all". CNet News. CBS Interactive. Retrieved November 28, 2010.
  13. ^ Crothers, Brooke (December 9, 2010). "Sources: 'Light Peak' technology not Apple idea". CNet News. CBS Interactive. Retrieved February 23, 2011.
  14. ^ Shah, Agam (January 8, 2011). "Intel says Light Peak interconnect technology is ready". Computer World. International Data Group. Retrieved February 23, 2011.
  15. ^ "IPtronics Develops Components for Light Peak Technology" (Press release). IPtronics. October 1, 2009. Retrieved April 5, 2011.
  16. ^ Clarke, Peter (October 1, 2009). "IPtronics, Avago chip in to Intel's optical interconnect". EETimes. Retrieved October 1, 2009.
  17. ^ a b c d e Dilger, Daniel Eran (February 24, 2011). "Intel details Thunderbolt, says Apple has full year head start". AppleInsider. Retrieved February 25, 2011.
  18. ^ a b Metz, Cade (February 24, 2011). "Intel: 'PC makers took the light out of Light Peak'". The Register. Situation Publishing. Retrieved February 25, 2011.
  19. ^ Jason Ziller (January 23, 2010). Light Peak to Connect Consumer Devices at Record Speed (YouTube). Intel. Event occurs at 1:13. Retrieved February 23, 2011.
  20. ^ Crothers, Brooke (February 19, 2011). "New high-speed connection tech due from Apple". CNet News. CBS Interactive. Retrieved February 25, 2011.
  21. ^ Kim, Arnold (February 19, 2011). "Apple to Introduce Light Peak (High Speed Connection Technology) Soon?". MacRumors. Retrieved February 25, 2011.
  22. ^ "Apple - Thunderbolt: Next-Generation high-speed I/O technology". Apple. February 24, 2011. Retrieved February 25, 2011.
  23. ^ "Apple Announces New iMac With Next Generation Quad-Core Processors, Graphics & Thunderbolt I/O Technology". Apple. Retrieved 10 May 2011.
  24. ^ Shah, Agam (April 12, 2011). "Intel to Open up Thunderbolt Development This Quarter". PC World. PCWorld Communications. Retrieved April 13, 2011.
  25. ^ Holland, Colin (April 12, 2011). "LeCroy lines up armada for Thunderbolt testing". EE Times Products. UBM Electronics. Retrieved April 18, 2011.
  26. ^ Nilsson, LG (February 25, 2011). "Intel announces Thunderbolt". VR-Zone. VR Media. Retrieved February 27, 2011.
  27. ^ Graham, Robert (February 24, 2011). "Thunderbolt: Introducing a new way to hack Macs". Errata Security. Retrieved March 5, 2011.
  28. ^ Perenson, Melissa J. (January 6, 2009). "SuperSpeed USB 3.0: More Details Emerge". PCWorld. IDG. Retrieved March 5, 2011.
  29. ^ Hewlett-Packard; Intel; Microsoft; NEC; ST-NXP Wireless; Texas Instruments (November 12, 2008), "Universal Serial Bus 3.0 Specification", Universal Serial Bus 3, USB, pp. 4–17 http://www.usb3.com/whitepapers/USB%203%200%20(11132008)-final.pdf, archived from the original (ZIP) on February 25, 2011, retrieved February 25, 2011 {{citation}}: Missing or empty |title= (help)
  30. ^ Lowensohn, Josh (February 24, 2011). "Intel fires up its Thunderbolt tech (live blog)". CNet News. CBS Interactive. Retrieved February 25, 2011.
  31. ^ Shilov, Anton (February 28, 2011). "AMD Does Not Believe in Intel's Thunderbolt". XBit Labs. Retrieved 2 March 2011.
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