Editing Microprocessor (section)

===8-bit designs===
{{More citations needed|section and the sections below|date=June 2011}}

The [[Intel 4004]] was followed in 1972 by the [[Intel 8008]], intel's first [[8-bit]] microprocessor.<ref>{{Cite web|title=Intel Microprocessor Quick Reference Guide - Year|url=https://www.intel.com/pressroom/kits/quickrefyr.htm|access-date=2021-09-21|website=www.intel.com|archive-date=6 October 2021|archive-url=https://web.archive.org/web/20211006020846/https://www.intel.com/pressroom/kits/quickrefyr.htm|url-status=live}}</ref> The 8008 was not, however, an extension of the 4004 design, but instead the culmination of a separate design project at Intel, arising from a contract with [[Datapoint|Computer Terminals Corporation]], of San Antonio TX, for a chip for a terminal they were designing,<ref name="mit-comp-history">{{cite book | last = Ceruzzi | first = Paul E. | title = A History of Modern Computing | edition = 2nd | date = May 2003 | publisher = MIT Press | isbn = 978-0-262-53203-7 | pages = [https://archive.org/details/historyofmodernc00ceru_0/page/220 220–221] | url = https://archive.org/details/historyofmodernc00ceru_0/page/220 }}</ref> the [[Datapoint 2200]]—fundamental aspects of the design came not from Intel but from CTC. In 1968, CTC's Vic Poor and Harry Pyle developed the original design for the [[instruction set]] and operation of the processor. In 1969, CTC contracted two companies, [[Intel]] and [[Texas Instruments]], to make a single-chip implementation, known as the CTC 1201.<ref name="forgotten-history">{{cite magazine |url=http://www.computerworld.com/s/article/9111341/Forgotten_PC_history_The_true_origins_of_the_personal_computer |title=Forgotten history: the true origins of the PC |first=Lamont |last=Wood |date=August 2008 |magazine=Computerworld |archive-url=https://web.archive.org/web/20220606084706/http://www.computerworld.com/s/article/print/9111341/Forgotten_PC_history_The_true_origins_of_the_personal_computer?taxonomyName=Hardware&taxonomyId=12 |archive-date=2022-06-06 |access-date=2011-01-07 |url-status=dead }}</ref> In late 1970 or early 1971, TI dropped out being unable to make a reliable part. In 1970, with Intel yet to deliver the part, CTC opted to use their own implementation in the Datapoint 2200, using traditional TTL logic instead (thus the first machine to run "8008 code" was not in fact a microprocessor at all and was delivered a year earlier). Intel's version of the 1201 microprocessor arrived in late 1971, but was too late, slow, and required a number of additional support chips. CTC had no interest in using it. CTC had originally contracted Intel for the chip, and would have owed them {{US$|50,000|1971}} for their design work.<ref name="forgotten-history"/> To avoid paying for a chip they did not want (and could not use), CTC released Intel from their contract and allowed them free use of the design.<ref name="forgotten-history"/> Intel marketed it as the 8008 in April, 1972, as the world's first 8-bit microprocessor. It was the basis for the famous "[[Mark-8]]" computer kit advertised in the magazine ''[[Radio-Electronics]]'' in 1974. This processor had an 8-bit data bus and a 14-bit address bus.<ref>Intel 8008 data sheet.</ref>

The 8008 was the precursor to the successful [[Intel 8080]] (1974), which offered improved performance over the 8008 and required fewer support chips. Federico Faggin conceived and designed it using high voltage N channel MOS. The [[Zilog Z80]] (1976) was also a Faggin design, using low voltage N channel with depletion load and derivative Intel 8-bit processors: all designed with the methodology Faggin created for the 4004. [[Motorola]] released the competing [[Motorola 6800|6800]] in August 1974, and the similar [[MOS Technology 6502]] was released in 1975 (both designed largely by the same people). The 6502 family rivaled the Z80 in popularity during the 1980s.

A low overall cost, little packaging, simple [[computer bus]] requirements, and sometimes the integration of extra circuitry (e.g. the Z80's built-in [[memory refresh]] circuitry) allowed the [[home computer]] "revolution" to accelerate sharply in the early 1980s. This delivered such inexpensive machines as the Sinclair [[ZX81]], which sold for {{US$|99|1981}}. A variation of the 6502, the [[MOS Technology 6510]] was used in the [[Commodore 64]] and yet another variant, the 8502, powered the [[Commodore 128]].

[[Western Design Center|The Western Design Center, Inc]] (WDC) introduced the CMOS [[WDC 65C02]] in 1982 and licensed the design to several firms. It was used as the CPU in the [[Apple IIe]] and [[Apple IIc|IIc]] personal computers as well as in medical implantable grade [[pacemaker]]s and [[defibrillator]]s, automotive, industrial and consumer devices. WDC pioneered the licensing of microprocessor designs, later followed by [[Arm Holdings|ARM]] (32-bit) and other microprocessor [[intellectual property]] (IP) providers in the 1990s.

Motorola introduced the [[Motorola 6809|MC6809]] in 1978. It was an ambitious and well thought-through 8-bit design that was [[source compatible]] with the [[Motorola 6800|6800]], and implemented using purely [[electrical wiring|hard-wired]] logic (subsequent 16-bit microprocessors typically used [[microcode]] to some extent, as [[complex instruction set computer|CISC]] design requirements were becoming too complex for pure hard-wired logic).

Another early 8-bit microprocessor was the [[Signetics 2650]], which enjoyed a brief surge of interest due to its innovative and powerful [[instruction set architecture]].

A seminal microprocessor in the world of spaceflight was [[RCA]]'s [[RCA 1802]] (aka CDP1802, RCA COSMAC) (introduced in 1976), which was used on board the ''[[Galileo (spacecraft)|Galileo]]'' probe to Jupiter (launched 1989, arrived 1995). RCA COSMAC was the first to implement [[CMOS]] technology. The CDP1802 was used because it could be run at very [[low-power electronics|low power]], and because a variant was available fabricated using a special production process, [[silicon on sapphire]] (SOS), which provided much better protection against [[cosmic radiation]] and [[electrostatic discharge]] than that of any other processor of the era. Thus, the SOS version of the 1802 was said to be the first [[radiation-hardened]] microprocessor.

The RCA 1802 had a [[static logic (digital logic)|static design]], meaning that the [[clock frequency]] could be made arbitrarily low, or even stopped. This let the [[Galileo (spacecraft)|''Galileo'' spacecraft]] use minimum electric power for long uneventful stretches of a voyage. Timers or sensors would awaken the processor in time for important tasks, such as navigation updates, attitude control, data acquisition, and radio communication. Current versions of the Western Design Center 65C02 and 65C816 also have [[static core]]s, and thus retain data even when the clock is completely halted.