Editing S-100 bus (section)

==History==
[[File:Cromemco XXU S-100 processor.jpg|thumb|The Cromemco XXU processor board, introduced in 1986. At 16.7 MHz, it is the fastest CPU ever developed for the {{nowrap|S-100}} bus. It uses a Motorola 68020 processor with 68881 co-processor and 16 Kbytes of high-speed cache memory. This CPU is used in the Cromemco CS-250 computer, widely deployed by the U.S. Air Force.]] 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 Roberts (computer engineer)|Ed Roberts]], 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 is split into four separate cards, with the [[Central processing unit|CPU]] on a fifth. He then looked for an inexpensive source of connectors, and he came across a supply of military surplus 100-pin [[edge connector]]s. The 100-pin bus was created by an unknown draftsman at MITS, who selected the connector from a parts catalog and arbitrarily assigned [[signal (electrical engineering)|signal]] names to groups of connector pins.<ref>{{cite magazine| url=https://books.google.com/books?id=aj4EAAAAMBAJ&pg=PT54 |title=The {{nowrap|S-100}} Bus: Past, Present, and Future |magazine=InfoWorld |date=February 18, 1980 |pages=7,18 |first=Sol |last=Libes |volume=2 |issue=1}}</ref>

A burgeoning industry of "clone" machines followed the introduction of the Altair in 1975. Most of these used the same bus layout as the Altair, creating a new industry standard. These companies were forced to refer to the system as the "Altair bus", and wanted another name in order to avoid referring to their competitor when describing their own system. The "{{nowrap|S-100}}" name, short for "Standard 100", was coined by [[Harry Garland]] and [[Roger Melen]], co-founders of [[Cromemco]].<ref>{{cite book |last1=Freiberger |first1=Paul |author-link1=Paul Freiberger |last2=Swaine |first2=Michael | author-link2=Michael Swaine (technical author) |year=2000 |title=Fire in the Valley: The Making of the Personal Computer |url=https://archive.org/details/fireinvalleymaki00frei |url-access=registration |edition=Second | publisher=McGraw-Hill |isbn=0-07-135892-7 | page=[https://archive.org/details/fireinvalleymaki00frei/page/66 66]}}</ref><ref>{{cite journal|title=The Cromemco Story|journal=I/O News|date=September–October 1980|volume=1|issue=1|pages=10|url=https://archive.org/stream/IoNewsVolume1Number1/CromemcoIoNews11Sep-oct1980#page/n5/mode/2up|access-date=2013-02-22}}</ref> While on a flight to attend the Atlantic City PC '76 microcomputer conference in August 1976, they shared the cabin with Bob Marsh and [[Lee Felsenstein]] of [[Processor Technology]]. Melen went over to them to convince them to adopt the same name. He had a beer in his hand and when the plane hit a bump, Melen spilt some of the beer on Marsh. Marsh agreed to use the name, which Melen ascribes to him wanting to get Melen to leave with his beer.<ref>{{cite book |title= Fire in the Valley: The Birth and Death of the Personal Computer |first1= Michael |last1=Swaine |first2=Paul |last2=Freiberger |url=https://books.google.com/books?id=-g5QDwAAQBAJ&q=processor+technology#q=beer|isbn= 9781680503524 |date= 2014-10-20 }}</ref>

The term first appeared in print in a Cromemco advertisement in the November 1976 issue of [[Byte (magazine)|Byte magazine]].<ref name=herb>Herbert Johnson, [http://retrotechnology.com/herbs_stuff/s_origins.html "Origins of {{nowrap|S-100}} computers"], 15 March 2008</ref> The first symposium on the {{nowrap|S-100}} bus, moderated by [[Jim Warren (computer specialist)|Jim Warren]], was held November 20, 1976 at [[Diablo Valley College]] with a panel consisting of [[Harry Garland]], [[George Morrow (computers)|George Morrow]], and [[Lee Felsenstein]].<ref>
{{Cite journal
 | journal = Homebrew Computer Club Newsletter | title = Random Data | author = Robert Reiling
 | volume = 2
 | page = 1
 |issue = 11–12
 | date = December 10, 1976
 | url = http://www.digibarn.com/collections/newsletters/homebrew/V2_11-12/Homebrew_CC_Dec76_Page_01.jpg
 }}</ref> Just one year later, the {{nowrap|S-100}} Bus would be described as "the most used busing standard ever developed in the computer industry."<ref>{{cite book|last=Zaks|first=Rodnay|title= Microprocessors - From Chips to Systems| publisher=Sybex| year = 1977|page=302}}</ref>

[[Cromemco]] was the largest of the {{nowrap|S-100}} manufacturers, followed by [[Vector Graphic]] and [[North Star Computers]].<ref>{{cite journal|last=Libes|first=Sol|journal=Microsystems|date=September–October 1981|volume=2|issue=5|title=The leaders in the {{nowrap|S-100}} marketplace are Cromemco ($50M), Vector Graphics ($30M) and North Star ($25M)|page=8}}</ref> Other innovators were companies such as [[Alpha Microsystems]], [[IMS Associates, Inc.]], Godbout Electronics (later [[Bill Godbout|CompuPro]]), and [[Ithaca InterSystems]]. In May 1984, ''Microsystems'' published a comprehensive {{nowrap|S-100}} product directory listing over 500 "{{nowrap|S-100}}/IEEE-696" products from over 150 companies.<ref name="Sol">{{cite journal|last=Libes|first=Sol|title={{nowrap|S-100}} Product Directory|journal=Microsystems|date=May 1984|volume=5|issue=5|pages=59–78}}</ref>

The {{nowrap|S-100}} bus signals were simple to create using an 8080 CPU, but increasingly less so when using other processors like the 68000. More board space was occupied by signal conversion logic. Nonetheless by 1984, eleven different processors were hosted on the {{nowrap|S-100}} bus, from the 8-bit Intel 8080 to the 16-bit Zilog [[Zilog Z8000|Z-8000]].<ref name="Sol"/> In 1986, Cromemco introduced the XXU card, designed by Ed Lupin, utilizing a 32-bit [[Motorola]] [[68020]] processor.<ref>{{cite journal|title=New XXU Processor Offers Enormous Speed Advantage|journal=I/O News|date=August–September 1986|volume=5|issue=4|pages=1,9 | issn=0274-9998 |url=https://archive.org/details/IoNewsVolume5Number4/mode/1up}}</ref>