Group:
computer hardware
Topic:
channel multiplexing
Topic:
communication protocols
Topic:
computer architecture
Topic:
distributed process control
Topic:
IEEE488 instrument bus
Topic:
implementing distributed systems and applications
Topic:
interprocess communication
Topic:
massively parallel processors
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Summary
Distributed control requires communication hardware and protocols to interconnect each computer. A multi-drop data bus is popular due to lower cabling costs. The network may be a multi-drop communications bus or a hierarchical system with radial components. The centralization of hierarchical/radial systems result in higher cabling costs, lower reliability, and better maintainability.
Standards are desirable because a network may contain hardware from different manufacturers. Hardware standards include ASCII standard, Intel's Multi-bus, Mostek's STD, H.-P.'s IEEE 488, Atomic Energy Commission's CAMAC, SDLC/HDLC, and Honeywell's Data-highway. Each standard specifies required hardware and communication protocols. Hardware is usually compatible with one or more standards. Implementation of the standard allows for hardware variation. CAMAC is a high-performance standard and expensive to implement. XEROX PARC uses a simple cable with a multi-master broadcast protocol. PIDCOM uses ASCII serial lines. (cbb 5/80)
Subtopic: Ethernet 
| Quote: with Ethernet, the error rates are very low; normal loads have few collisions; heavy loads are handled well [»shocJF12_1980]
| | Quote: an Ethernet interface board can have serious hardware problems yet perform well; due to high-level protocols for fault handling [»liskB10_1981]
| | Quote: on the Ethernet, lack of a carrier is a hint that a packet can be sent [»lampBW10_1983]
| | Quote: Clearinghouse at Xerox: several hundred ethernets and several thousand workstations, servers and hosts [»demeA8_1987]
| | Quote: broadcast is seldom used in ethernet because everyone must process it; too slow [»giffDK7_1985, OK]
| | Quote: a Xerox subsidiary sells addresses for ethernet [»giffDK7_1985, OK]
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Subtopic: industrial control networks
| Quote: BARNACLE uses a data and control line and allows wide variation in clock skew and frequency [»brooRA_1987]
| | Quote: for digital flight-control use synchronous channels, sensor data to all channels, and exact-match majority voting; needs fault-tolerant clock synchronization, etc. [»rushJ12_1991]
| | Quote: the lack of standard communication protocols have kept vendors away from distributed network design [»instrumentcontrol]
| | Quote: PIDCOM uses serial links and ASCII to communicate with its analog controllers [»washJ3_1978]
| | QuoteRef: instrumentcontrol ;;9/79 70 Edelman S: "A joint development by Mostek and Pro- Log, the STD is exciting because, according to OEM suppliers and users, it's simpler, smaller, and lower in cost than Intel's Multibus. /8-bit orientation with single master built on 4.5 x 6.5" cards
| | QuoteRef: washJ3_1978 ;;Title: Communications interface primer
| | QuoteRef: washJ3_1978 ;;45 CAMAC parallel interface standard (IEEE) in 66-wire fully parallel with 24 data bits, or 9-pair byte serial for transmitting 24 bit words by threes, or 2-wire serial interface. Devices organized into standard remote interface units called crates.
| | QuoteRef: washJ3_1978 ;;61 "Regardless of which controller is used, every CAMAC crate has an 86-point connector called a Dataway. This Dataway can accommodate up to 25 modules along with a power supply. Any module made to CAMAC specifications-- from A/D multiplexers to color CRT display drives--can plug into the CAMAC crate, regardless of its manufacturer.
| | QuoteRef: washJ3_1978 ;;62 "Ease of use along with CAMAC's speed make it a top of the line interface. It is, however, expensive. /COMAC 2-wire serial highway can transmit up to 5 megabaud, making it of the fastest serial interfaces available/
| | QuoteRef: washJ3_1978 ;;63 SDLC and HDLC data link protocols for networking. eg used in Honeywell's TDC-200 data highway (well almost the same).
| | QuoteRef: washJ3_1978 ;;64 "SLDC and HLDC are by far the most efficient protocols available today...However, data link protocols are more expensive to implement because an intelligent controller must be installed in each remote station.
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Subtopic: digital switching
| Quote: ITT 1240 uses the digital switching network for inter-process communication and voice channels; 64 kbit/sec channels [»bonaR_1981]
| | Quote: ITT 1240's digital switching network must be controlled at its inlets; otherwise processors need other control elements to set up paths [»bonaR_1981]
| | Quote: ITT 1240's digital switching network needs to be virtually nonblocking; otherwise interprocess communication slowed down [»bonaR_1981]
| | Quote: ITT 1240's digital switching network needs path setup within 1 or 2 milliseconds; otherwise message delays would effect exchange response time [»bonaR_1981]
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Subtopic: Connection Machine
| Quote: the physical connectivity of the Connection Machine is controlled by software; in order to match problem's structure [»hillWD_1985]
| | Quote: when message delivered to a router, corresponding address bit is cleared; all done when address is 0 [»hillWD_1985]
| | Quote: a CM-1 prototype achieved 10^10 bits/sec random-message bandwidth; for local traffic expect 4x larger bandwidth [»hillWD_1985]
| | Quote: the Connection Machine handles message congestion by referring messages to adjoining routers; one step further from destination [»hillWD_1985]
| | Quote: a hashnet is a random network topology; does well compared to proposed networks and easy to analyze [»hillWD_1985]
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Subtopic: wiring
| Quote: can connect controllers by a device highway or a nest highway to "nests" of controllers [»instrumentcontrol]
| | QuoteRef: instrumentcontrol ;;12/78 42 LaBarge DL & Levine:"Radial and hierarchical networks also have similar disadvantages-- high installation cost and the dangers of dependence on higher network levels.
| | Quote: cabling is often the second largest cost of a network (computer system cost is first) [»instrumentcontrol]
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Subtopic: bus vs. serial
| Quote: it is easy to write to a bus and hard to read a bus; perform a read by writing a request to write the data; thus, a read in two writes; e.g., DMA channels [»duvaVJ9_1997]
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Subtopic: interrupt control
| Quote: hardware timer interrupts are expensive; context switch, highest priority, poor cache locality [»aronM8_2000]
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Related Topics
Group: computer hardware (24 topics, 343 quotes)
Topic: channel multiplexing (3 items)
Topic: communication protocols (62 items)
Topic: computer architecture (46 items)
Topic: distributed process control (6 items)
Topic: IEEE488 instrument bus (2 items)
Topic: implementing distributed systems and applications (41 items)
Topic: interprocess communication (29 items)
Topic: massively parallel processors
(29 items)
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