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	Topics S-100 bus Topic Home The S-100 bus, IEEE696-1983 (withdrawn), was an early computer busComputer bus In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or... designed in 1974 as a part of the Altair 8800Altair 8800 The MITS Altair 8800 was a microcomputer design from 1975, based on the Intel 8080A CPU.... , generally considered today to be the first personal computerFacts About Personal computer A personal computer is usually a microcomputer whose price, size, and capabilities make it suitable for personal usage.... (or at least the first "microcomputer", insofar as it was designed for hobbyists rather than the general public). The S-100 bus was the first industry standard bus for the microcomputerMicrocomputer Although there is no rigid definition, a microcomputer is most often taken to mean a computer with a microprocessor as its... industry. S-100 computers, consisting of processor and peripheral cards, were produced by a number of manufacturers. The S-100 bus formed the basis for homebrew computers whose builders (e.g., the Homebrew Computer ClubHomebrew Computer Club The Homebrew Computer Club was an early computer hobbyist club in Silicon Valley, which met from March 1975 to roughly 1977.... ) implemented drivers for CP/MCP/M CP/M is an operating system originally created for Intel 8080/85 and Zilog Z80 based microcomputers by Gary Kildall of Digit... and MP/MMP/M MP/M was the multi-user version of the CP/M operating system, created by Digital Research.... . These S-100 microcomputers ran the gamut from hobbyist toy to small business workstation and were the zenith of the microcomputer world until the advent of the IBM PCIBM PC Summary The IBM PC , was the original version and progenitor of the IBM PC compatible hardware platform.... (which some of them outperformed). Architecture The S-100 bus essentially consisted of the pins of the Intel 8080Intel 8080 The Intel 8080 was an early microprocessor designed and manufactured by Intel.... run out onto the backplaneBackplane A backplane is a circuit board that connects several connectors in parallel to each other, so that each pin of each connect... . No particular level of thought went into the design, leading to such disasters as various power lines of differing voltages being located next to each other, resulting in easy shortingShort circuit A short circuit is an accidental low-resistance connection between two nodes of an electrical circuit that are meant to be a... . The system included two unidirectional 8 bit data buses, but only a single bidirectional 16 bit address bus. A deal on power supplies led to the use of +8 V and +/- 18 V, which had to be "regulated downVoltage regulator A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level.... " on the cards to TTLFacts About Transistor-transistor logic Transistor-Transistor Logic is a class of digital circuits built from bipolar junction transistors , and resistors.... (+5 V) and RS-232 (+/-12 V) levels. History During the design of the Altair, the hardware required to make a usable machine was not available in time for the January 1975 launch date. The designer, Ed RobertsEd Roberts Ed Roberts is...* A disability-rights activist and founder of the disability rights movement... , also had the problem of the backplane taking up too much room. Attempting to avoid these problems, he placed the existing components in a case with additional "slots", so that the missing components could be plugged in later when they became available. The backplane was split into four separate cards, with the CPUCentral processing unit A central processing unit , or sometimes simply processor, is the component in a digital computer that interprets ins... on a fifth. He then looked for a cheap source of connectors, and he came across a supply of 100-pin edge connectorEdge connector An edge connector is the portion of a printed circuit board consisting of traces leading to the edge of the board that are i... s. Another designer who did a great deal to push the S-100 technology forward was George MorrowGeorge Morrow (computers) George Morrow was part of the early microcomputer industry in the United States.... , with his company Morrow Designs. Morrow was the first chairman of the S-100 Bus Standards Committee, which later became IEEE-696. Other innovators were companies such as IMS Associates, Inc.Facts About IMS Associates, Inc. IMS Associates, Inc. was a computer company responsible for one of the earliest successes in personal computing, the IMSAI 8... , CromemcoCromemco Cromemco was a Mountain View, California microcomputer company that began as a partnership in 1974 between Harry Garland and... , Godbout Electronics (later CompuPro), and Ithaca IntersystemsIthaca Intersystems Ithaca Intersystems was a microcomputer manufacturer in the 1970s and 1980s, located in Ithaca, New York USA.... . The standards committee introduced the 16-bit data bus to the S-100, which had up to then supported only 8-bit data, by using the two separate uni-directional data buses as a single bi-directional bus. The S-100 bus has a number of variants from different manufacturers, but had eventually been standardized as IEEE-696 towards the end of 1983. By this point the S-100 bus had evolved into the standard for all "professional" personal computers, almost all of them running CP/MCP/M CP/M is an operating system originally created for Intel 8080/85 and Zilog Z80 based microcomputers by Gary Kildall of Digit... . The standard was so powerful that many other CPU designs were either made to "look" like the 8080 (most notably the Zilog Z80Zilog Z80 Summary The Zilog Z80 is an 8-bit microprocessor designed and sold by Zilog from July 1976 onwards.... ), or otherwise placed on complex converter cards to allow them to be plugged into S-100 machines. Notable S-100 bus computer users Among the most notable users of S-100 busus computers was science fictionScience fiction Science fiction is a popular genre of fiction in which the narrative world differs from our own present or historical reali... writer and Byte magazine columnist Jerry PournelleJerry Pournelle Jerry Pournelle, is an American essayist, journalist and science fiction author who contributed for many years to the compu... , who wrote many of his early novels on an S-100 bus machine running CP/M he dubbed "Zeke", which is now on display in the Smithsonian. External links Focusing on Cromemco and other S-100 manufacturers.