RapidIO
Encyclopedia
The RapidIO architecture is a high-performance packet-switched
, interconnect
technology for interconnecting chips
on a circuit board
, and also circuit boards to each other using a backplane
. This technology is designed specifically for embedded system
s, primarily for the signal processing
, networking, and communications
markets.
RapidIO is intended to be the optimal interconnect when clustering networks of peer to peer embedded processors, DSPs
, FPGA
s and ASIC
s. RapidIO has found widespread adoption in the following applications:
The main competing technology is PCI Express
, but PCI Express is targeted at the desktop and high performance computing arenas, as opposed to embedded systems. PCIe does not scale as well in large multiprocessor peer to peer systems as RapidIO as the memory map for PCIe using non transparent bridging is not as simple as RapidIO which uses a push architecture where each endpoint can have its own memory system
RapidIO was developed by Mercury Computer Systems
and Motorola
(now Freescale Semiconductor
), primarily as an upgraded interconnect for Mercury's embedded NUMA
/cluster ("multicomputer") signal processing computers.
There are two incarnations of RapidIO Technology: Parallel RapidIO and Serial RapidIO (SRIO). The main difference between the two is that Parallel RapidIO has a separate clock signal
, while Serial RapidIO uses clock recovery in the receiver to generate a clock from the data stream. 8B/10B encoding
is used in the transmitter to ensure DC balance and enough edge density to recover the clock. With respect to actual deployment in both silicon and system level
products, Serial RapidIO has had the most traction and is used in all the switches, DSPs, microprocessors and FPGAs widely available on the market today.
Packets are big-endian, 256 bytes, with 8-bit or 16-bit addresses, and routed
by crossbar switch
es. Links are point-to-point, with handshaking
and reservations to ensure that packets need not be dropped. Links are commonly half-duplex parallel Low voltage differential signaling
or serial
fiber optic. Special signaling allows timestamp
s to flood fill
through the fabric without concern for packet boundaries. RapidIO is designed to support memory mapping
, mailbox
queues, and doorbell-style interrupts.
RapidIO serial links can be driven at different baud rates. RapidIO 1.2 and 1.3 support 1.25, 2.5 and 3.125 Gbaud rates. RapidIO 1.2/1.3 support x1 and x4 link configurations, for a maximum rate of 12.5 Gbaud which equates to a 10 Gbit/s data rate when 8b/10b encoding is removed. With RapidIO Gen 2, 5 Gbaud and 6.25 Gbaud rates are added. The RapidIO Gen 2 specifications support x1, x2, x4, x8 and x16 link configurations.
Standards released by the RapidIO Trade Association include RapidIO 1.2, RapidIO 1.3, RapidIO 2.0. and RapidIO 2.1. Specifications beyond RapidIO 2.1 are currently in development.
. Ericsson
, Freescale Semiconductor
, IDT
, Texas Instruments
, and Xilinx
comprise the Steering Committee of the RapidIO Trade Association.
, PICMG
and the Mountain View Alliance
.
Packet switching
Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network...
, interconnect
Electrical connection
An electrical connection between discrete points allows the flow of electrons . A pair of connections is needed for a circuit.Between points with a low voltage difference, direct current can be controlled by a switch...
technology for interconnecting chips
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
on a circuit board
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
, and also circuit boards to each other using a backplane
Backplane
A backplane is a group of connectors connected in parallel with each other, so that each pin of each connector is linked to the same relative pin of all the other connectors forming a computer bus. It is used as a backbone to connect several printed circuit boards together to make up a complete...
. This technology is designed specifically for embedded system
Embedded system
An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...
s, primarily for the signal processing
Signal processing
Signal processing is an area of systems engineering, electrical engineering and applied mathematics that deals with operations on or analysis of signals, in either discrete or continuous time...
, networking, and communications
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
markets.
RapidIO is intended to be the optimal interconnect when clustering networks of peer to peer embedded processors, DSPs
Digital signal processor
A digital signal processor is a specialized microprocessor with an architecture optimized for the fast operational needs of digital signal processing.-Typical characteristics:...
, FPGA
Field-programmable gate array
A field-programmable gate array is an integrated circuit designed to be configured by the customer or designer after manufacturing—hence "field-programmable"...
s and ASIC
Application-specific integrated circuit
An application-specific integrated circuit is an integrated circuit customized for a particular use, rather than intended for general-purpose use. For example, a chip designed solely to run a cell phone is an ASIC...
s. RapidIO has found widespread adoption in the following applications:
- Wireless base stations
- Military single-board computerSingle-board computerA single-board computer is a complete computer built on a single circuit board, with microprocessor, memory, input/output and other features required of a functional computer. Unlike a typical personal computer, an SBC may not include slots into which accessory cards may be plugged...
s, as well as Radar, Acoustic and Image Processing Systems - Video
- Server
- Medical imagingMedical imagingMedical imaging is the technique and process used to create images of the human body for clinical purposes or medical science...
- Industrial applications
The main competing technology is PCI Express
PCI Express
PCI Express , officially abbreviated as PCIe, is a computer expansion card standard designed to replace the older PCI, PCI-X, and AGP bus standards...
, but PCI Express is targeted at the desktop and high performance computing arenas, as opposed to embedded systems. PCIe does not scale as well in large multiprocessor peer to peer systems as RapidIO as the memory map for PCIe using non transparent bridging is not as simple as RapidIO which uses a push architecture where each endpoint can have its own memory system
RapidIO was developed by Mercury Computer Systems
Mercury Computer Systems
Mercury Computer Systems, Inc. provides high-performance embedded, real-time digital signal and image processing solutions.Mercury designs and builds embedded multicomputers, which may be considered to be either loosely coupled NUMA computers or tightly coupled clusters. Despite being marketed as...
and Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
(now Freescale Semiconductor
Freescale Semiconductor
Freescale Semiconductor, Inc. is a producer and designer of embedded hardware, with 17 billion semiconductor chips in use around the world. The company focuses on the automotive, consumer, industrial and networking markets with its product portfolio including microprocessors, microcontrollers,...
), primarily as an upgraded interconnect for Mercury's embedded NUMA
Non-Uniform Memory Access
Non-Uniform Memory Access is a computer memory design used in Multiprocessing, where the memory access time depends on the memory location relative to a processor...
/cluster ("multicomputer") signal processing computers.
Technology
The RapidIO specification is a packet-based technology defined for endpoints, which originate and process packets and switches, which are used to connect endpoints. RapidIO is a layered specification, intuitively divided into a physical layer protocol, packet transport (routing) protocol and multiple protocols at the logical layer. Multiple logical layer protocols define different methods by which endpoints can exchange data. The transport layer defines how all RapidIO packets are routed through a RapidIO switch. The physical layer defines the electrical characteristics and link layer packet transfer protocol that all RapidIO endpoints and switches must follow to guarantee interoperability.There are two incarnations of RapidIO Technology: Parallel RapidIO and Serial RapidIO (SRIO). The main difference between the two is that Parallel RapidIO has a separate clock signal
Clock signal
In electronics and especially synchronous digital circuits, a clock signal is a particular type of signal that oscillates between a high and a low state and is utilized like a metronome to coordinate actions of circuits...
, while Serial RapidIO uses clock recovery in the receiver to generate a clock from the data stream. 8B/10B encoding
8B/10B encoding
In telecommunications, 8b/10b is a line code that maps 8-bit symbols to 10-bit symbols to achieve DC-balance and bounded disparity, and yet provide enough state changes to allow reasonable clock recovery. This means that the difference between the count of 1s and 0s in a string of at least 20 bits...
is used in the transmitter to ensure DC balance and enough edge density to recover the clock. With respect to actual deployment in both silicon and system level
System-level solution
A system-level solution is a set of integrated circuits that work together to power an application such as a mobile telephone or digital media player. A special case of a system-level solution is a system-on-a-chip, where the entire functionality of the system is integrated into a single chip....
products, Serial RapidIO has had the most traction and is used in all the switches, DSPs, microprocessors and FPGAs widely available on the market today.
Packets are big-endian, 256 bytes, with 8-bit or 16-bit addresses, and routed
Routing
Routing is the process of selecting paths in a network along which to send network traffic. Routing is performed for many kinds of networks, including the telephone network , electronic data networks , and transportation networks...
by crossbar switch
Crossbar switch
In electronics, a crossbar switch is a switch connecting multiple inputs to multiple outputs in a matrix manner....
es. Links are point-to-point, with handshaking
Handshaking
In information technology, telecommunications, and related fields, handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel begins...
and reservations to ensure that packets need not be dropped. Links are commonly half-duplex parallel Low voltage differential signaling
Low voltage differential signaling
Low-voltage differential signaling, or LVDS, is an electrical digital signaling system that can run at very high speeds over inexpensive twisted-pair copper cables. It was introduced in 1994, and has since become very popular in computers, where it forms part of very high-speed networks and...
or serial
Serial communications
In telecommunication and computer science, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where several bits are sent as a whole, on a link with several parallel channels...
fiber optic. Special signaling allows timestamp
Timestamp
A timestamp is a sequence of characters, denoting the date or time at which a certain event occurred. A timestamp is the time at which an event is recorded by a computer, not the time of the event itself...
s to flood fill
Flood fill
Flood fill, also called seed fill, is an algorithm that determines the area connected to a given node in a multi-dimensional array. It is used in the "bucket" fill tool of paint programs to determine which parts of a bitmap to fill with color, and in games such as Go and Minesweeper for determining...
through the fabric without concern for packet boundaries. RapidIO is designed to support memory mapping
Memory mapping
In computing, memory mapping may refer to:* Memory-mapped file, also known as mmap* Memory-mapped I/O, an alternative to port I/O; a communication between CPU and peripheral device using the same instructions, and same bus, as between CPU and memory...
, mailbox
Mailbox
Mailbox may refer to:* Letter box, copper box, or other sturdy material compartment, or slot for incoming postal deliveries.* Post box, a physical box for outgoing postal deliveries....
queues, and doorbell-style interrupts.
RapidIO serial links can be driven at different baud rates. RapidIO 1.2 and 1.3 support 1.25, 2.5 and 3.125 Gbaud rates. RapidIO 1.2/1.3 support x1 and x4 link configurations, for a maximum rate of 12.5 Gbaud which equates to a 10 Gbit/s data rate when 8b/10b encoding is removed. With RapidIO Gen 2, 5 Gbaud and 6.25 Gbaud rates are added. The RapidIO Gen 2 specifications support x1, x2, x4, x8 and x16 link configurations.
Standards released by the RapidIO Trade Association include RapidIO 1.2, RapidIO 1.3, RapidIO 2.0. and RapidIO 2.1. Specifications beyond RapidIO 2.1 are currently in development.
RapidIO Trade Association
Industry leaders in networking, communications, semiconductors, and embedded systems have founded the RapidIO Trade Association to develop and support this international open standardOpen standard
An open standard is a standard that is publicly available and has various rights to use associated with it, and may also have various properties of how it was designed . There is no single definition and interpretations vary with usage....
. Ericsson
Ericsson
Ericsson , one of Sweden's largest companies, is a provider of telecommunication and data communication systems, and related services, covering a range of technologies, including especially mobile networks...
, Freescale Semiconductor
Freescale Semiconductor
Freescale Semiconductor, Inc. is a producer and designer of embedded hardware, with 17 billion semiconductor chips in use around the world. The company focuses on the automotive, consumer, industrial and networking markets with its product portfolio including microprocessors, microcontrollers,...
, IDT
Integrated Device Technology
Integrated Device Technology, Inc. is a publicly traded corporation headquartered in San Jose, California, that designs, manufactures, and markets low-power, high-performance mixed-signal semiconductor solutions for the advanced communications, computing, and consumer industries. The company...
, Texas Instruments
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
, and Xilinx
Xilinx
Xilinx, Inc. is a supplier of programmable logic devices. It is known for inventing the field programmable gate array and as the first semiconductor company with a fabless manufacturing model....
comprise the Steering Committee of the RapidIO Trade Association.
Liaisons
The RapidIO Trade Association has numerous liaisons with other industry groups including the Optical Internetworking ForumOptical Internetworking Forum
The Optical Internetworking Forum is a non-profit, member-driven organization founded in 1998. It promotes the development and deployment of interoperable networking solutions and services through the creation of Implementation Agreements for optical networking products, network processing...
, PICMG
PICMG
The PCI Industrial Computer Manufacturers Group is a consortium of over 227 companies. The group, founded in 1994, was originally formed to adapt PCI technology for use in high-performance telecommunications, military and industrial computing applications but its work has now grown to include...
and the Mountain View Alliance
Mountain View Alliance
The Mountain View Alliance is a consortium of consortia announced in June 2005 and intended to enable the adoption of commercial off-the-shelf solutions through coordination of marketing activities...
.