View source for KIM-1

== 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.