THUNDERBOLT - Seminar Paper

INTRODUCTION

The present era is the era of connectivity. Think of any sort of information, and it can be transferred to us within question of a little time; be it audio information, video information or any other form of data.

Now talking about transferring data between our computer and the other peripherals, the first and foremost standard comes to our mind is Universal Serial Bus (USB). It is a medium speed serial data addressable bus system which carry large amount of data to a relatively short distance (up to 5m).The present version USB 3.0 promises to provide theoretical speed of up to 5Gbps.

But Intel has unveiled a new interoperable standard called THUNDERBOLT(Light Peak) which can transfer data between computers and the peripherals at the speed of 10Gbps in both the directions with maximum range of  100m (much higher than USB or any other standard) and has potential to scale its speed high up to 100Gbps in near future.

Light Peak is the code name for thunderbolt technology, a new high-speed optical cable technology designed to connect electronic devices to each other.

It is basically an optical cable interface designed to connect devices in peripheral bus. It is being developed as a single universal replacement for the current buses such as SCSI, SATA, USB, FireWire, PCIExpress, and HDMI etc in an attempt to reduce the proliferation of ports on computers.

Fiber-optic cabling is not new, but Intel executives believe Thunderbolt will make it cheap enough and small enough to be incorporated into consumer electronics at a price point that consumers and manufacturers will accept.

Thus with thunderbolt, the bandwidth would tremendously increase, multiple protocols could be run over single longer and thinner cable.

The prototype system featured two motherboard controllers that both supported two bidirectional buses at the same time, wired to four external connectors. Each pair of optical cables from the controllers is led to a connector, where power is added through separate wiring. The physical connector used on the prototype system looks similar to the existing USB or FireWire connectors.

Intel has stated that this technology has the performance to drive everything from storage to displays to networking, and it can maintain those speeds over 100 meter runs. 

Thunderbolt began at Intel Labs with a simple concept: create an incredibly fast input/output technology that just about anything can plug into. After close technical collaboration between Intel and Apple, Thunderbolt emerged from the lab to make its first appearance in MacBook Pro.

Intel co-invented USB and PCI Express, which have become widely adopted technologies for data transfer. Apple invented FireWire and was instrumental in popularizing USB. Their collective experience has made Thunderbolt the most powerful, most flexible I/O technology ever in a personal computer.

THUNDERBOLT TECHNOLOGY 

Developed by Intel (under the code name Light Peak), and brought to market with technical collaboration from Apple. Thunderbolt technology is a new, high-speed, dual-protocol I/O technology designed for performance, simplicity, and flexibility. This high-speed data transfer technology features the following:

· Dual-channel 10 Gbps per port

· Bi-directional

· Dual-protocol (PCI Express* and Display port*)

· Compatible with existing Display Port devices

· Daisy-chained devices

· Electrical or optical cables

· Low latency with highly accurate time synchronization

· Uses native protocol software drivers

· Power over cable for bus-powered devices

Intel's Thunderbolt controllers interconnect a PC and other devices, transmitting and receiving packetized traffic for both PCIe and DisplayPort protocols. Thunderbolt technology works on data streams in both directions, at the same time, so users get the benefit of full bandwidth in both directions, over a single cable. With the two independent channels, a full 10 Gbps of bandwidth can be provided for the first device, as well as additional downstream devices.

Thunderbolt 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 line up on February 24, 2011, using the same port and connector as Mini Display Port. Though initially registered with Apple Inc., full rights of the Thunderbolt technology trademark belong to Intel Corp., and subsequently led to the transfer of the registration.

Thunderbolt essentially combines PCI Express and Display Port 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 Display Port hardware upstream of the driver.

The interface was originally intended to run on an optical physical layer using components and flexible optical fiber cabling developed by Intel partners and at Intel's Silicon Photonics lab. The Intel technology at the time was marketed under the name Light Peak,[6] today (2011) referred to as Silicon Photonics Link.[7] However, conventional copper wiring turned out to be able to furnish the desired 10 Gb/s Thunderbolt bandwidth at lower cost. Later versions of Thunderbolt are still planned to introduce an optical physical layer based on Intel silicon photonics technology.

Thunderbolt is a revolutionary I/O technology that supports high-resolution displays and high-performance data devices through a single, compact port. It sets new standards for speed, flexibility, and simplicity. And it makes its debut in the new MacBook Pro.

POWERFULL TECHNOLOGY  FROM A POWERFULL COLABORATION

Thunderbolt began at Intel Labs with a simple concept: create an incredibly fast input/output technology that just about anything can plug into. After close technical collaboration between Intel and Apple, Thunderbolt emerged from the lab to make its first appearance in MacBook Pro.

Intel co-invented USB and PCI Express, which have become widely adopted technologies for data transfer. Apple invented FireWire and was instrumental in popularizing USB. Their collective experience has made Thunderbolt the most powerful, most flexible I/O technology ever in a personal computer.

PERFORMANCE AND EXPANSION NEVER SEEN ON A NOTEBOOK BEFORE

Thunderbolt I/O technology gives you two channels on the same connector with 10 Gbps of throughput in both directions. That makes it ultra fast, and ultra flexible. You can move data to and from peripherals up to 20 times faster than with USB 2.0 and more than 12 times faster than with FireWire 800. You also have more than enough bandwidth to daisy-chain multiple high-speed devices, without using a hub or switch. For example, you can connect several high-performance external disks, a video capture device, and even a Mini Display Port display to a single Thunderbolt chain while maintaining maximum throughput.

THUNDERBOLT TECHNOLOGY FEATURES

Optical networking technologies have been over the last two decades reshaping the entire telecom infrastructure networks around the world and as network bandwidth requirements increase, optical communication and networking technologies have been moving from their telecom origin into the enterprise and  Thunderbolt is one of its successful outcome.

 It is basically a new high-speed optical cable technology designed to connect electronic devices to each other.  It also support multiple protocols simultaneously with the bidirectional speed of about 10Gbps (can scale up to about 100Gbps). In comparison to other bus standards like SATA and HDMI, it is much faster, smaller, longer ranged, and more flexible in terms of protocol support. 

Thus it basically provides:

Standard low cost high bandwidth optical-based interconnect.

Supports multiple existing I/O protocols and smooth transition between them.

Supports wide range of devices (handhelds, PCs, workstations etc.)

Connect to more devices with the same cable, or to combo devices such as docking stations.

Smaller connectors.

Longer (up to 100m on single cable), thinner and economical.

Thunderbolt consist of a controller chip and optical module that would be included in platform to support this technology. The optical module performs the task of conversion of electricity to light conversion and vice versa, using miniature lasers and photo detectors. This transceiver can send two channels of information over an optical cable, necessary, since pc needs at least two ports.  The controller chip provides protocol switching to support multiple protocols over single cable.    

The Thunderbolt cable contains a pair of optical fibers that are used for upstream and downstream traffic to provide speed of about 10Gbps in both the directions.

The prototype system featured two motherboard controllers that both supported two bidirectional buses at the same time, wired to four external connectors. Each pair of optical cables from the controllers is led to a connector, where power is added through separate wiring.

It was developed as a way to reduce proliferation of number of ports on the modern computer. Earlier USB was developed for the same purpose and performed very well in the direction but increased bandwidth demand and high performance has led to development of new more efficient technologies.

Combining the high bandwidth of optical fiber with Intel’s practice to multiplex multiple protocols over a single fiber, optical technology may change the landscape of IO system design in the future. It’s possible that most of the legacy IO protocols can be tunneled by optical-capable protocols, so some of the legacy IO interfaces can be converged to one single optical interface, significantly simplifying the form factor design of computers. This change in IO system will definitely affect the design of systems.

There are four main components in this figure, the IO devices, the IO controller which connects to the IO devices through optical fiber, the processing unit and the interconnection between the IO controller and the processing unit, whatever it can be implemented as.

Mobile and handheld devices are two fast growing market segments which attract interests from processor vendors. For mobile and handheld devices, user interface and IO are two important factors besides computing power that affect end users’ purchase decision. Taking power into account, it’s possible that more carefully tuned IO workload offloading engines will be integrated into the IO controller, saving the power to move the data from IO a long way to the system memory. It makes no sense to have a high throughput IO system with insufficient processing power or overloaded interconnections between IO system and the processor.

The ultimate goal of system architects is to make a balanced and efficient system, on both power and cost grounds.

TODAYS CHALLENGES

In the coming future, people would be using more and more electrical devices such as HD devices, MIDs and many more and user experience would depend on the huge volume of data capturing, transfer, storage, and reconstruction. But existing electrical cable technology is approaching the practical limit for higher bandwidth and longer distance, due to the signal degradation caused by electro-magnetic interference (EMI) and signal integrity issues.

Higher bandwidth can be achieved by sending the signals down with more wires, but apparently this approach increases cost, power and difficulty of PCB layout, which explains why serial links such as SATA, SAS, and USB are becoming the mainstream.

However optical communications do not create EMI by using photonics rather than electrons, thus allowing higher bandwidth and longer distances. Besides, optical technology also allows for small form factors and longer, thinner cables.

Electrons v/s Photons

The physics has a kind of inevitability about it. Electrons travel through copper more slowly than light through fiber. The USB connectors on the smaller devices like mobile phones have to use mini-USB or micro-USB to save on the space taken up by the wiring and electricity through wire creates electric field interference, but light do not create EMI since it rely over photonics. Optical connecters can carry extremely narrow beams of light and fiber can be thinner because more streams can pass through glass or plastic passages. Each fiber is only 125 microns wide, the width of a human hair.

In the present scenario, the devices are getting smaller, thinner, and lighter but present connecting standards seems to hinder in their performance being to thicker and stiffer. So vendors turn over to new technologies providing much better performance and Thunderbolt seems to be a providing a good solution.

Different protocols demands for different connectors leading to too many connectors and cables. But in Thunderbolt there is the Thunderbolt protocol and the native protocols such as PCI Express, DisplayPort, USB or whatever might be running on it. The native protocols run basically on top of the Thunderbolt protocol. But the Thunderbolt protocol defines the speed. The protocol is running at 10 gigabits per second. So, if the native protocols that are running on top of it are also running at 10 gigabits per second, or something close to that, then the effective bandwidth for a device on the other end would be equivalent to that 10Gbps.

Thus, it can be said that presently we demand for the devices and technologies that:

Provides much higher bandwidth 

Provides more flexible designs, thinner form factor and new and better usage models.

Much simpler and easier in terms of connectivities.

It’s possible that most of the legacy IO protocols can be tunneled by optical-capable protocols, so some of the legacy IO interfaces can be converged to one single optical interface, significantly simplifying the form factor design of computers. This change in IO system will definitely affect the design of systems. It makes no sense to have a high throughput IO system with insufficient processing power or overloaded interconnections between IO system and the processor. Ultimately the main aim is to built an efficient and balanced system.

Thus Thunderbolt seems to be providing a good solution to the problems existing with the copper connectors and provides a good platform for the high performance system.

THUNDERBOLT V/S USB 3.0

USB 3.0

It is an electrical cable technology which transmits data using electricity which put limitation on speed and length. 

It consists of 9 copper wires for transfer of data between the PC and the peripherals.

Theoretically it can provide maximum speed of 5Gbps which on practical grounds get restricted to about 3Gbps.

It supports only USB protocol.

The maximum allowable cable length for USB 3.0 is only about nine meters 

THUNDERBOLT 

It is an optical cable technology which relies over light to transmit data thus providing much better speed and length.

It consists of 4 optical fibers for both upstream and downstream traffic simultaneously.

Initial proposed speed for Thunderbolt (LPK) [10] starts at 10Gbps and has future potential to scale up to 100Gbps. With this speed Blu-Ray movie can be transferred in less than 30 seconds (or in less than 3 seconds with 100Gbps).

It is a Universal connector supporting multiple existing protocols.

The maximum allowable cable length is about 100 meters and can be even extended more.

COMPONENTS OVERVIEW

Thunderbolt consists of a controller chip and an optical module that would be included in platforms supporting this technology. The optical module performs the conversion from electricity to light and vice versa, using miniature lasers (VCSELs) and photo detectors. Intel is planning to supply the controller chip, and is working with other component manufacturers to deliver all the Thunderbolt components. The main components are:

Fiber optics

Optical module

Controller chip

THUNDERBOLT TECHNOLOGY OVERVIEW

Thunderbolt Technology is an optical cable technology that consists of an optical module and controller chip which allows multiple protocols to run over the single cable. From the technical point of view, Intel’s Thunderbolt Technology can be overviewed as:

Thunderbolt protocol

Thunderbolt controller

Thunderbolt platforms

Server Network

THUNDERBOLT PROTOCOL ARCHITECTURE

Efficient transport mechanism:

It uses packet switch multiplexing. 

Packetize data to transfer

Multiplex it onto the wire

Packets from different connections share the same link.

Each packet is composed by the payload (the data we want to transmit) and a header. The header contains information useful for transmission, such as:

      • Source (sender’s) address

• Destination (recipient’s) address

• Packet size

• Sequence number

• Error checking information

Thunderbolt Networks use a similar idea of packet switching.

All the IO devices may have their native protocols but when using Thunderbolt they all run over Thunderbolt protocol. That is they uses their individual protocol for data transfer but their speed is defined by Thunderbolt.

Also it uses Virtual Wire Semantics thus performs high level of isolation between high level protocols (QoS). 

It provides cheap switching and establishes all routing at the setup only.

THUNDERBOLT CONTROLLER

At the heart of Thunderbolt is an Intel-designed controller chip that handles the protocols, along with an optical module that converts electrical signals to photons and vice versa. 

Basic implementation unit of Thunderbolt Controller contains:

A Cross bar switching unit: switches the various protocols from LPK to their respective protocol adapter.

LPK Ports and Protocol Adapter ports: LPK ports to connect down to PC using any standard and diverging it their respective protocol through protocol adapter.

The Host controller is typically multi protocol and has multiple ports with a software interface unit and is optimized for host side implementation whereas the peripheral controller could be single port and single protocol-based and is optimized for particular usage.

This is because of this controller chip that different protocols get identified and transmitted  correctly. API (Application programming interface) helps to determine the different protocols. It places the FIS (Flag Identification Symbol) packets in the memory, the controller access these packets from the memory and send these packets to the destination over the optical link.  

The multi-protocol capability the controller implements is an innovative new technology that will enable new usage models like flexible system designs and thinner form factors, media creation and connectivity, faster media transfer and cable simplification.

BRINGING OPTICAL TO MAINSTREAM

Since Thunderbolt is developed to meet PC requirements and the telecom ones, thus the Thunderbolt optical module can be designed to be lower cost than Telecom optical modules. This is due to some modification in design considerations:

First Intel relaxed the optical standards required of its components. In the telecom market, components must meet stringent Telcordia standards, such as a 20-year lifetime. Obviously, that kind of longevity is not required in the PC market, so Intel lowered its requirements to a five- to seven-year lifetime.

· Requirements for the operating environment also are not as rigorous. Intel lowered thermal requirements from the Telcordia-specified range of 0° to 85° to a more relaxed 5° to 65°. Intel had originally intended to specify a range starting at 0° but then realized that batteries freeze at that temperature, making the operation of the PC a moot point.

The company also relaxed its specification for number of failures per lifetime. If there is a failure on a trans-Atlantic cable, it’s a big deal. But the potential failure of one of four ports on a PC, for example, is not nearly as critical.

Because Thunderbolt is intended for distances of 100 m or less—and dispersion is, therefore, not an issue—spectral-width requirements also can be less stringent than Telcordia specifies. As a result vendors are able to get closer to 90% to 95% yields on their VCSELs and photo detectors, rather than the much lower in telecom.”

Intel has also removed the traditional eye-safety requirements, which also translates into higher yields and lower costs. The traditional telecom module is typically launched at about 1 mW of power. But the very aggressive power management of the Thunderbolt optical module features a launch power much higher than eye safety. 

Finally, Intel designed the optical module to be high-volume manufacturable thus further reducing the cost of production.

ADVANTAGES

• The Thunderbolt optical modules are physically much smaller than those of telecom grade.
• The optical modules are designed to be much lower cost and higher performance.
• Thunderbolt can send and receive data at 10 billion bits per second.
• The thin optical fiber will enable Thunderbolt to transfer data over very thin, flexible cables. 
• Unlike electrical cables, Thunderbolt do not faces the problem of EMI, thus can be used up to 100m.
• Thunderbolt also has the ability to run multiple protocols simultaneously over a single cable, enabling the technology to connect devices such as docking stations, displays, disk drives, and more. A simple analogy is it is like loading up many cars onto a high-speed bullet train. 
• The data transfer is bidirectional in nature thus enabling devices to transfer simultaneously. 
• Quality of service implementation
• No Operating System (OS) changes required.
• It also supports another feature known as “Hot-swapping” which means the PC needs not be shut down and restarted to attach or remove a peripheral.
• Economies of scale from a single optical solution 
• Enables I/O performance for the next generation Allows for balanced platform, with external I/O keeping up with most platform interconnects.
• Up to 100 meters on an optical-only cable. Each fiber is only 125 microns wide, the width of a human hair.
• Supports multiple existing I/O protocols over a single cable and smooth transition for today’s existing electrical I/O protocols.
• Can connect to more devices with the same cable, or to combo devices such as docking stations.                    

CONCLUSION

Thunderbolt is a high-speed, multi-protocol interconnect for innovative and emerging client usage models, that complements other existing interconnects

Thunderbolt is the name for a new high-speed optical cable technology designed to connect electronic devices to each other. Thunderbolt delivers high bandwidth starting at 10Gb/s with the potential ability to scale to 100Gb/s over the next decade. At 10Gb/s, we can transfer a full-length Blu-Ray movie in less than 30 seconds.  Thunderbolt allows for smaller connectors and longer, thinner, and more flexible cables than currently possible. Thunderbolt also has the ability to run multiple protocols simultaneously over a single cable, enabling the technology to connect devices such as peripherals, displays, disk drives, docking stations, and more.