QuickRing
Encyclopedia
QuickRing was a gigabit-rate interconnect that combined the functions of a computer bus
and a network
. It was designed at Apple Computer
as a multimedia system to run "on top" of existing local bus
systems inside a computer, but was later taken over by National Semiconductor
and repositioned as an interconnect for parallel computing. It appears to have seen little use in either role, and is no longer being actively worked on. However it appears to have been an inspiration for other more recent technologies, such as HyperTransport
.
project, which started in the late 1970s under the aegis of the IEEE. Realizing Futurebus was doomed, several of the main designers left the effort in 1987 to try again on smaller projects, leading to both QuickRing and SCI
. In the case of QuickRing the main proponent was Paul Sweazey of National Semiconductor
, who had hosted Futurebus's cache
coherency group. Sweazey left National Semiconductor and moved to Apple Computer
's Advanced Technology Group, where the new system was developed.
The system was first announced publicly at the 1992 Worldwide Developers Conference
, positioned primarily as a secondary bus for computer systems to carry multiple streams of digital video
without using the existing backplane
bus. Apple was particularly interested in this role due to the limitations of their current NuBus
systems in terms of speed. They envisioned various video cards using a second connector located near the "top" (opposite the NuBus connector) to talk to each other. Optionally, one of the cards would produce compressed output, which could be sent over the NuBus for storage or display. Before any commercial use of QuickRing, newer versions of PCI
started appearing that offered performance close enough to QuickRing to make its role redundant. Apple switched to an all-PCI based computer lineup starting in 1995, and in one of their general downsizings in the early 90s, Apple dropped their funding for QuickRing.
In response Sweazey moved back to National Semiconductor, who positioned QuickRing as a high-speed interconnect. Here it had little better luck, competing against SCI
on one hand, and ever-faster versions of Ethernet
on the other. Efforts were made to standardize QuickRing inside the existing VMEbus
system using some redundant pins in response to an industry effort to standardize parallel processing hardware, but nothing ever came of this. The US Navy announced several tenders for QuickRing products for sonar
data processing (for which they had originally had Futurebus+ developed), but it is unclear whether or not it was used in this role. National eventually lost interest, and the system essentially disappeared in 1996. Similar products, notablty SKYconnect and Raceway
, were also standardized in this role, but seem to have seen little use as well.
links carrying data, and one extra line carrying a 50 MHz clock signal. Apple's implementation consisted of six data lines and the clock line using twisted-pair copper wiring (using LVDS) embedded in a thin plastic strip. National Semiconductor offered a variety of different implementations with up to 32 data lines, as well as the same signals multiplexted using frequency-division multiplexing
in a single fibre optic cable for longer links between machines.
The data lines were clocked at seven times the clock signal, so each clock "tick" moved 7 bit
s of data over each of the bus lines. For the Apple implementation this meant 7 bits times 6 links at 50 million times a second, for a raw data rate of 2.1 Gbit
/s. Ten bits of the 42 were used for signalling and control, leaving 32 for data, resulting in a net data transfer rate of 1.6 Gbit/s, or 200 MB
/s. This was only slightly faster than contemporary (1993) versions of PCI at ~130 MB/s, but much faster than NuBus of the same era, at about 20 MB/s.
Each QuickRing interface contained two such links, one for "upstream" and one for "downstream" connections in a point-to-point ring. Since the system was not a bus, machines could talk up and downstream at the same time without interfering with other users. The drawback was that each hop over an intervening point added a latency of up to 1.3 µs. Since QuickRing was built in a ring topology there was no need for a dedicated switch or router, potentially making the system lower cost to deploy. Two rings could be connected together by putting the bus IC's "back to back" in a switch, allowing for larger networks.
QuickRing routing used a circuit switching
system, in which the message path is set up before the data is sent, and once set up the connection is very lightweight. This is as opposed to packet switching
, in which every message contains all of the data needed to reach the destination, this is more flexible, but adds overhead. Of the 10 bits of control data, four were used to specify a circuit number, allowing for a total of 16 devices per ring.
Computer bus
In computer architecture, a bus is a subsystem that transfers data between components inside a computer, or between computers.Early computer buses were literally parallel electrical wires with multiple connections, but the term is now used for any physical arrangement that provides the same...
and a network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....
. It was designed at Apple Computer
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
as a multimedia system to run "on top" of existing local bus
Local bus
In computer science, a local bus is a computer bus that connects directly, or almost directly, from the CPU to one or more slots on the expansion bus. The significance of direct connection to the CPU is avoiding the bottleneck created by the expansion bus, thus providing fast throughput...
systems inside a computer, but was later taken over by National Semiconductor
National Semiconductor
National Semiconductor was an American semiconductor manufacturer, that specialized in analog devices and subsystems,formerly headquartered in Santa Clara, California, USA. The products of National Semiconductor included power management circuits, display drivers, audio and operational amplifiers,...
and repositioned as an interconnect for parallel computing. It appears to have seen little use in either role, and is no longer being actively worked on. However it appears to have been an inspiration for other more recent technologies, such as HyperTransport
HyperTransport
HyperTransport , formerly known as Lightning Data Transport , is a technology for interconnection of computer processors. It is a bidirectional serial/parallel high-bandwidth, low-latency point-to-point link that was introduced on April 2, 2001...
.
History
QuickRing started as an offshoot of the fabled FuturebusFuturebus
Futurebus is a computer bus standard, intended to replace all local bus connections in a computer, including the CPU, memory, plug-in cards and even, to some extent, LAN links between machines. The effort started in 1979 and didn't complete until 1987, and then immediately went into a redesign...
project, which started in the late 1970s under the aegis of the IEEE. Realizing Futurebus was doomed, several of the main designers left the effort in 1987 to try again on smaller projects, leading to both QuickRing and SCI
Scalable Coherent Interconnect
SCI, for Scalable Coherent Interface, is a high-speed interconnect standard for shared memory multiprocessing and message passing. The IEEE Std 1596-1992, IEEE Standard for Scalable Coherent Interface was approved by the IEEE standards board on March 19, 1992...
. In the case of QuickRing the main proponent was Paul Sweazey of National Semiconductor
National Semiconductor
National Semiconductor was an American semiconductor manufacturer, that specialized in analog devices and subsystems,formerly headquartered in Santa Clara, California, USA. The products of National Semiconductor included power management circuits, display drivers, audio and operational amplifiers,...
, who had hosted Futurebus's cache
Cache
In computer engineering, a cache is a component that transparently stores data so that future requests for that data can be served faster. The data that is stored within a cache might be values that have been computed earlier or duplicates of original values that are stored elsewhere...
coherency group. Sweazey left National Semiconductor and moved to Apple Computer
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
's Advanced Technology Group, where the new system was developed.
The system was first announced publicly at the 1992 Worldwide Developers Conference
Worldwide Developers Conference
The Apple Worldwide Developers Conference, commonly abbreviated WWDC, is a conference held annually in California by Apple Inc. The conference is primarily used by Apple to showcase its new software and technologies for developers, as well as offering hands-on labs and feedback sessions...
, positioned primarily as a secondary bus for computer systems to carry multiple streams of digital video
Digital video
Digital video is a type of digital recording system that works by using a digital rather than an analog video signal.The terms camera, video camera, and camcorder are used interchangeably in this article.- History :...
without using the existing 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...
bus. Apple was particularly interested in this role due to the limitations of their current NuBus
NuBus
NuBus is a 32-bit parallel computer bus, originally developed at MIT as a part of the NuMachine workstation project. The first complete implementation of the NuBus and the NuMachine was done by Western Digital for their NuMachine, and for the Lisp Machines Inc. LMI-Lambda. The NuBus was later...
systems in terms of speed. They envisioned various video cards using a second connector located near the "top" (opposite the NuBus connector) to talk to each other. Optionally, one of the cards would produce compressed output, which could be sent over the NuBus for storage or display. Before any commercial use of QuickRing, newer versions of PCI
Peripheral Component Interconnect
Conventional PCI is a computer bus for attaching hardware devices in a computer...
started appearing that offered performance close enough to QuickRing to make its role redundant. Apple switched to an all-PCI based computer lineup starting in 1995, and in one of their general downsizings in the early 90s, Apple dropped their funding for QuickRing.
In response Sweazey moved back to National Semiconductor, who positioned QuickRing as a high-speed interconnect. Here it had little better luck, competing against SCI
Scalable Coherent Interconnect
SCI, for Scalable Coherent Interface, is a high-speed interconnect standard for shared memory multiprocessing and message passing. The IEEE Std 1596-1992, IEEE Standard for Scalable Coherent Interface was approved by the IEEE standards board on March 19, 1992...
on one hand, and ever-faster versions of Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
on the other. Efforts were made to standardize QuickRing inside the existing VMEbus
VMEbus
VMEbus is a computer bus standard, originally developed for the Motorola 68000 line of CPUs, but later widely used for many applications and standardized by the IEC as ANSI/IEEE 1014-1987. It is physically based on Eurocard sizes, mechanicals and connectors , but uses its own signalling system,...
system using some redundant pins in response to an industry effort to standardize parallel processing hardware, but nothing ever came of this. The US Navy announced several tenders for QuickRing products for sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...
data processing (for which they had originally had Futurebus+ developed), but it is unclear whether or not it was used in this role. National eventually lost interest, and the system essentially disappeared in 1996. Similar products, notablty SKYconnect and Raceway
Raceway
Raceway may refer to:* Race track, a place where races are run or operated* In construction projects, a surface mounted wire moulding* A mill race, the current or channel of a stream...
, were also standardized in this role, but seem to have seen little use as well.
Description
The basic QuickRing system consisted of a number of single-direction 1-bit serialSerial 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...
links carrying data, and one extra line carrying a 50 MHz clock signal. Apple's implementation consisted of six data lines and the clock line using twisted-pair copper wiring (using LVDS) embedded in a thin plastic strip. National Semiconductor offered a variety of different implementations with up to 32 data lines, as well as the same signals multiplexted using frequency-division multiplexing
Frequency-division multiplexing
Frequency-division multiplexing is a form of signal multiplexing which involves assigning non-overlapping frequency ranges to different signals or to each "user" of a medium.- Telephone :...
in a single fibre optic cable for longer links between machines.
The data lines were clocked at seven times the clock signal, so each clock "tick" moved 7 bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s of data over each of the bus lines. For the Apple implementation this meant 7 bits times 6 links at 50 million times a second, for a raw data rate of 2.1 Gbit
Gigabit
The gigabit is a multiple of the unit bit for digital information or computer storage. The prefix giga is defined in the International System of Units as a multiplier of 109 , and therefore...
/s. Ten bits of the 42 were used for signalling and control, leaving 32 for data, resulting in a net data transfer rate of 1.6 Gbit/s, or 200 MB
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
/s. This was only slightly faster than contemporary (1993) versions of PCI at ~130 MB/s, but much faster than NuBus of the same era, at about 20 MB/s.
Each QuickRing interface contained two such links, one for "upstream" and one for "downstream" connections in a point-to-point ring. Since the system was not a bus, machines could talk up and downstream at the same time without interfering with other users. The drawback was that each hop over an intervening point added a latency of up to 1.3 µs. Since QuickRing was built in a ring topology there was no need for a dedicated switch or router, potentially making the system lower cost to deploy. Two rings could be connected together by putting the bus IC's "back to back" in a switch, allowing for larger networks.
QuickRing routing used a circuit switching
Circuit switching
Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the...
system, in which the message path is set up before the data is sent, and once set up the connection is very lightweight. This is as opposed to packet switching
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...
, in which every message contains all of the data needed to reach the destination, this is more flexible, but adds overhead. Of the 10 bits of control data, four were used to specify a circuit number, allowing for a total of 16 devices per ring.
Further reading
- The QuickRing Network, M. Valerio, L. E. Moser, P. M. Melliar-Smith and P. Sweazey, ACM Conference on Computer Science
External links
- Trevor Marshall, "Fast Transit", BYTE, October 1992
- "Whatever Happened to... QuickRing", BYTE, November 1994