IntroductionIntel 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. The system was driven by a prototype PCI Express card, with two optical buses powering four ports. At the show, Intel claimed that Light Peak-equipped systems would begin to appear in 2010.
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.
In September 2010, some early commercial prototypes from manufacturers were demonstrated at Intel Developer Forum 2010.
 Copper vs. opticalOriginally conceived as an optical technology, Thunderbolt switched to electrical connections to reduce costs and to supply up to 10W of power to connected devices.
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.” 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.”
In January 2011, Intel’s David Perlmutter told Computerworld that initial Thunderbolt implementations would be based on copper wires. “The copper came out very good, surprisingly better than what we thought,” he said.
Intel and industry partners are still developing optical Thunderbolt hardware and cables. The optical fiber cables are to run “tens of meters” but will not supply power, at least not initially. They are to have two 62.5-micron-wide fibers to transport an infrared signal up to 100 metres (330 ft). The conversion of electrical signal to optical will be embedded into the cable itself, allowing the current DisplayPort socket to be future compatible, but eventually Intel hopes for a purely optical transceiver assembly embedded in the PC.
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 (center port)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. 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. 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. 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 published  technical details explaining that 6 daisy-chained peripherals are supported per Thunderbolt port, and that the Display should lie at the end of the chain.
Thunderbolt adoption Model Transition date
MacBook Pro 2011-02-24
MacBook Air 2011-07-20
Mac mini 2011-07-20
Mac Pro N/A
In 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.
In May 2011, Apple announced a new line of iMacs that include 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 pin out as the legacy DisplayPort connector. The primary visual differentiation on Thunderbolt equipped Macs is a Thunderbolt symbol instead of a DisplayPort symbol next to the port opening. 
Apple’s legacy DisplayPort standard is partially compatible with Thunderbolt, as the two share the a physically compatible Mini DisplayPort connector. The Target Display mode on iMacs requires a Thunderbolt cable to accept a video-in signal from another Thunderbolt-capable computer.  Mini DisplayPort monitors function correctly as an external monitor without an adaptor if they are either the only or the last device in the Thunderbolt device chain.
Intel announced that a developer kit will be released in the second quarter of 2011, while manufacturers of hardware development equipment have indicated they will add support for the testing and development of Thunderbolt devices.
Thunderbolt will be featured on Intel’s Ivy Bridge, but it will not be integrated into its 7-series chipsets, scheduled for release around March 2012.
Thunderbolt link connections
Intel will provide two types of Thunderbolt controllers, a 2 port type and a 1 port type. Both Peripherals and computers need to include a controller.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. 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.
Thunderbolt controllers on the host and peripherals fold the PCIe and DisplayPort data together and unfold them after they exit the cable.
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.
 SecuritySee also: DMA attack
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. This issue exists with all high-speed expansion buses, including PC Card, ExpressCard and IEEE 1394 interface (FireWire).
It is worth noting that a number of Intel processors since the introduction of the Nehalem microarchitecture (that is, a number of CPU branded 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.