View source for KIM-1

{{Short description|Single-board computer produced by MOS Technology in 1976}}
{{About|a single-board computer|Kidney injury molecule-1|HAVCR1}}
{{Infobox information appliance
| name         = KIM-1
| logo         = 
| image        = MOS KIM-1 IMG 4211 cropped scale.jpg
| caption      = MOS KIM-1 computer. On display at the [[Musée Bolo]], [[École Polytechnique Fédérale de Lausanne|EPFL]], [[Lausanne]].
| aka          = 
| developer    = [[Chuck Peddle]]
| manufacturer = [[MOS Technology|MOS Technology, Inc.]]
| family       = 
| type         = [[single-board computer]]
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| cpu          = [[MOS Technology 6502|6502]]
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| website      = <!--{{URL|example.org}}-->
| title        = 
| releasedate  = {{Start date and age|1976}}
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}}
[[File:Kim-1-computer.jpg|thumb|right|KIM-1 computer in operation]]

The '''KIM-1''', short for ''Keyboard Input Monitor'', is a small [[MOS Technology 6502|6502]]-based [[single-board computer]] developed and produced by [[MOS Technology|MOS Technology, Inc.]] and launched in 1976. It was very successful in that period, due to its low price (thanks to the inexpensive 6502 microprocessor) and easy-access expandability.

== History ==
MOS Technology's first processor, the [[MOS Technology 6501|6501]], could be plugged into existing motherboards that used the [[Motorola 6800]], allowing potential users (i.e. engineers and hobbyists) to get a development system up and running very easily using existing hardware. [[Motorola]] immediately sued, forcing MOS to pull the 6501 from the market.  Changing the pin layout produced the "lawsuit-friendly" [[MOS Technology 6502|6502]]. Otherwise identical to the 6501, it nevertheless had the disadvantage of having no machine in which new users could quickly start using the [[central processing unit|CPU]].

[[Chuck Peddle]], leader of the 650x group at MOS (and former member of Motorola's 6800 team), designed the KIM-1 <ref name=Dillon2014> "Ready: A Commodore 64 Retrospective", Roberto Dillon, 2014 Springer ISBN  9789812873415, 9812873414 </ref> in order to fill this need. The KIM-1 came to market in 1976. While the machine was originally intended to be used by engineers, it quickly found a large audience with  hobbyists. A complete system could be constructed for under {{nowrap|US$500}} with the purchase of the computer itself for only {{nowrap|US$245}}, and then adding a power supply, a secondhand [[Character-oriented terminal|terminal]] and a [[Kansas City standard|cassette tape drive]].

Many books were available demonstrating small [[assembly language]] programs for the KIM, including ''The First Book of KIM'' by  [[Jim Butterfield]] ''et al''.<ref name="Butterfield, KIM, First Book of" >{{cite book
  |last=Butterfield |first=Jim |author-link=Jim Butterfield
  |year=1977
  |url=https://archive.org/stream/The_First_Book_of_KIM#page/n0/mode/2up
  |title=The First Book of KIM
  |first2=Stan |last2=Ockers |first3=Eric |last3=Rehnke
  |isbn=0-8104-5119-0
  |publisher=Hayden Book
}}</ref> One demo program converted the KIM into a music box by toggling a software-controllable output bit connected to a small [[loudspeaker]].  Canadian programmer [[Peter R. Jennings]] produced what was probably the first game for microcomputers to be sold commercially, ''[[Microchess]],'' originally for the KIM-1.

As the system became more popular, one of the common additions was the [[Tiny BASIC|Tiny BASIC programming language]]. This required an easy memory expansion; "all of the decoding for the first 4 K is provided right on the KIM board. All you need to provide is 4&nbsp;K more of RAM chips and some buffers."<ref>{{cite magazine
  |last = Simpson
  |first = Richard
  |title = A Date with KIM
  |url = https://archive.org/stream/byte-magazine-1976-05/1976_05_BYTE_00-09_Shooting_Stars#page/n9/mode/2up
  |journal = BYTE
  |volume = 1
  |issue = 9
  |pages = 14
  |publisher = Byte Publications
  |date = May 1976
}}</ref> The hard part was loading the BASIC from [[cassette tape]]—a 15-minute, error-prone ordeal.

[[Rockwell International]]—who second-sourced the 6502, along with [[Synertek]]—released their own microcomputer in one board in 1978, the [[AIM-65]].  The AIM included a full [[ASCII]] keyboard, a 20-character [[fourteen-segment display|14-segment]] [[alphanumeric]] [[light-emitting diode|LED]] display, and a small [[cash register]]-like printer.  A [[debugger|debug]] [[machine code monitor|monitor]] was provided as standard [[firmware]] for the AIM, and users could also purchase optional [[read-only memory|ROM]] chips with an [[Assembly language#Assembler|assembler]] and a [[Microsoft BASIC]] [[interpreter (computing)|interpreter]] to choose from.

Finally, there was the Synertek [[SYM-1]] variant, which could be said to be a machine halfway between the KIM and the AIM; it had the KIM's small display, and a simple [[membrane keyboard]] of 29 keys (hex digits and control keys only), but provided AIM-standard expansion interfaces and true [[RS-232]] (voltage level as well as current loop mode supported).

== Description ==
[[File:KIM-1 Computer Ad May 1976.jpg|thumb|upright|The introductory advertisement for the KIM-1 microcomputer, April 1976]]

The KIM-1 consisted of a single [[printed circuit board]] with all the components on one side. It included three main [[integrated circuit|ICs]]; the MCS6502 CPU and two [[MOS Technology RRIOT|MCS6530]] Peripheral Interface/Memory Devices.  Each MCS6530 comprises a mask programmable 1024 × 8 ROM, a 64 × 8 RAM, two eight-bit bi-directional ports, and a programmable interval timer.<ref>{{cite book
  |title = MCS6500 Microcomputer Family Hardware Manual
  |publisher = MOS Technology
  |date = January 1976
  |pages = 71
}}</ref> The KIM-1 brochure said "1&nbsp;K BYTE RAM" but it actually had 1152 bytes. The memory was composed of eight 6102 static RAMs (1024 × 1 bits) and the two 64-byte RAMs of the MCS6530s. In the 1970s memory sizes were expressed in several ways. Semiconductor manufacturers would use a precise memory size such as 2048 by 8 and sometimes state the number of bits (16384). Mini and mainframe computers had various memory widths (8 bits to over 36 bits) so manufacturers would use the term "words", such as 4K words. The early hobbyist computer advertisements would use both "words" and "bytes".  It was common to see "4096 words", "4K (4096) words" and "4&nbsp;K bytes". The term KB was unused or very uncommon.  The KIM-1 was introduced in the April 1976 issue of ''[[BYTE]]'' and the advertisement stated "1&nbsp;K BYTE RAM" and "2048 ROM BYTES".<ref>{{cite magazine
  |title = MOS KIM-1
  |journal = BYTE
  |url=https://archive.org/stream/byte-magazine-1976-04/1976_04_BYTE_00-08_Automation#page/n15/mode/2up
  |volume = 1
  |issue = 8
  |pages = 15
  |type = advertisement
  |publisher = Byte Publications
  |date = April 1976
}}</ref>

Also included were six [[seven-segment display|7-segment]] [[Light-emitting diode|LEDs]] (similar to those on a pocket [[calculator]]) and a 24-key calculator-type keypad.
Many of the pins of the I/O portions of the 6530s were connected to two connectors on the edge of the board, where they could be used as a [[serial communications|serial]] system for driving a [[Teletype Model 33]] ASR and [[paper tape|paper tape reader and punch]].

One of these connectors also doubled as the power supply connector and included analog lines that could be attached to a [[cassette tape]] recorder.

Earlier [[microcomputer]] systems such as the [[Altair 8800|MITS Altair]] used a series of switches on the front of the machine to enter data. In order to do anything useful, the user had to enter a small program known as the "bootstrap loader" into the machine using these switches, a process known as [[booting]]. Once loaded, the loader would be used to load a larger program off a storage device like a [[paper tape]] reader.  It would often take upwards of five minutes to load the tiny program into memory, and a single error while flipping the switches meant that the bootstrap loader would crash the machine. This could render some of the bootstrap code garbled, in which case the programmer had to reenter the whole thing and start all over again.

The KIM-1 included a somewhat more complex built-in Terminal Interface Monitor software called '''TIM''' that was "contained in 2048&nbsp;bytes of ROM in two 6530 ROM/RAM/IO arrays".<ref>{{cite magazine
  |title = What's New, KIM-o-sabee?
  |journal = BYTE
  |url=https://archive.org/stream/byte-magazine-1976-04/1976_04_BYTE_00-08_Automation#page/n15/mode/2up
  |volume = 1
  |issue = 8
  |pages = 14
  |publisher = Byte Publications
  |date = April 1976
}}</ref> This monitor software included the ability to run a cassette tape for storage, drive the LED display, and run the keypad. As soon as the power was turned on, the monitor would run and the user could immediately start interacting with the machine via the keypad. The KIM-1 was one of the first [[single-board computer]]s, needing only an external power supply to enable its use as a stand-alone experimental computer.  This fact, plus the relatively low cost of getting started, made it quite popular with hobbyists through the late 1970s.

== Video display ==
[[File:PAiA TVT-6 Video Display Dec 1977.jpg|thumb|upright|PAiA TVT-6 Video Display]]

The designer of the [[TV Typewriter]], [[Don Lancaster]], developed a low-cost video display for the KIM-1. The add-on board would display up to 4000 characters on a TV or monitor. A typical configuration would be 16 lines of 32 upper-case only characters. The board had only 10 low-cost ICs and used the KIM's memory for the screen storage.

The TVT-6 project appeared on the cover on ''[[Popular Electronics]]'' in July 1977.<ref>{{cite magazine |last= Lancaster |first= Don |url= https://archive.org/details/197707PopularElectronics/page/n41/mode/2up |author-link= Don Lancaster |title= Build the TVT-6: A Low-Cost Direct Video Display |journal= Popular Electronics |volume= 12 |issue= 1 |pages= 47–52 |publisher= Ziff-Davis Publishing  |date= July 1977}}</ref> The complete kit could be ordered from [[PAiA Electronics]] for {{US$|34.95}}.

Lancaster expanded this design to do color and simple graphics in ''The Cheap Video Cookbook''.<ref>{{cite book |last = Lancaster |first = Don |author-link = Don Lancaster |title = The Cheap Video Cookbook |publisher = Howard W Sams |year = 1978 |isbn = 0-672-21524-1}}</ref>

== Specifications ==
* CPU: [[MOS Technology 6502|MCS6502]] - clocked at 1&nbsp;MHz
* two PIO [[MOS Technology RRIOT|MCS6530]] - {{nowrap|1024 × 8 ROM}}, {{nowrap|64 × 8 RAM}}, two 8-bit [[General Purpose Input/Output|bi-directional ports]], 8-bit [[Programmable Interval Timer|programmable interval timer]]
* eight 6102 [[Static random access memory|static RAM]] - 1024 × 1 (1024&nbsp;bytes)
* six [[Seven-segment display|7-segment]] [[Light-emitting diode|LEDs]]
* 24-key calculator type [[keypad]]
* two [[serial communications|serial]] ports
* Terminal Interface Monitor (TIM), that handled [[booting]], keypad, seven-segment LEDs, and cassette tape

== Tape format ==
<!--Connected to application connector-->Each bit is represented by three 2.484&nbsp;ms long tones. The first is always 3700&nbsp;Hz, the middle is 3700&nbsp;Hz for "0" or 2400&nbsp;Hz for "1", and the last one is always 2400&nbsp;Hz. This gives an effective bit rate of 134.2&nbsp;bit/s. Detection is done through a [[Phase-locked loop|PLL]] using LM565.<!--Appendix E--><ref name="usrman1-kim1">{{cite web|title=Users Manual V1.0|url=https://users.telenet.be/kim1-6502/6502/usrman.html|archiveurl=https://web.archive.org/web/20220831224832/http://users.telenet.be/kim1-6502/6502/usrman.html|archive-date=31 August 2022}}</ref><!--Chapter 3, Audio tape interface, Figure 3.8, page 31-->

The format of data on the tape is: 100 bytes with the value 0x16 (SYN, Synchronous Idle), one byte with the value 0x2A (*), the record identification number, the start address (two characters for the low byte of address, two characters for the high byte), the end address (in the same format), the actual data, one byte with the value 0x2F ("/" character), a two-byte [[checksum]], and two bytes with the value 0x04 (EOT, End Of Transmission).<ref name="usrman1-kim1" />

Each byte of memory is stored as two sequential ASCII characters on tape, for example, [[hexadecimal]] B5 in memory (181 decimal) would be stored as two sequential ASCII characters "B" and "5" (42 and 35 hexadecimal).<ref name="usrman1-kim1" />

== See also ==
* [[Elektor Junior Computer]]
* [[Microprocessor development board]]
* [[MOS Technology file format]]

== References ==
{{Reflist}}

== External links ==
{{Commons category}}
* [https://www.oldcomputermuseum.com/kim_1.html KIM-1] and collection of old digital and analog computers at oldcomputermuseum.com
* {{webarchive |original-url=https://users.telenet.be/kim1-6502/ |url=https://web.archive.org/web/20220831205542/http://users.telenet.be/kim1-6502/ |title=KIM-1 6502 website |date=August 31, 2022}} – <kbd>erik.vdbroeck</kbd>'s resource site for the KIM-1, with several [[HTML]]'ized manuals and books
* [http://www.6502.org/trainers/buildkim/buildkim.htm Instructions on building your own KIM-1]
* [https://obsolescence.wixsite.com/obsolescence/kim-uno-summary-c1uuh KIM Uno], a KIM-1 emulator based on the [[Arduino]] Pro Mini

{{Commodore International}}
{{Authority control}}

[[Category:Commodore 8-bit computers]]
[[Category:Early microcomputers]]
[[Category:Computer-related introductions in 1976]]