Editing Mostek (section)

==Microprocessor second sourcing deals==
With this foundation in calculator chips and high volume DRAM production, Mostek gained a reputation as a leading semiconductor "fabrication house" ([[fab (semiconductors)|fab]]) in the early 1970s.

=== MK5065 ===
In 1974 Mostek introduced the [[Mostek 5065|MK5065]], an 8-bit PMOS [[microprocessor]], with 51 instructions whose execution times range from 3 to 16 μs. Architectural features included multiple nested indirect addressing and three register sets (each consisting of an accumulator, a program counter and a carry/link bit) which could be used for interrupt processing or for subroutines.<ref>{{cite journal |title=Mostek 5065's by the 1000's |journal=Microcomputer Digest |date=February 1975 |volume=8 |issue=8 |pages=1–2 |url=http://www.bitsavers.org/magazines/Microcomputer_Digest/Microcomputer_Digest_v01n08_Feb75.pdf |access-date=10 January 2021 |publisher=Microcomputer Associates Inc}}</ref><ref>{{cite book |title=Integrated Circuit Guide |publisher=Mostek |date=1974 |pages=78–80 |url=https://archive.org/details/bitsavers_mostekdatagratedCircuitGuide_14005467/page/n79 |access-date=2021-11-04}}</ref><ref>Mostek 5065 instruction set: {{cite book |title=A Microcomputer Based Substation Control System |author=Billy Don Russel, Jr. |date=1975 |pages=108–112 |publisher=University of Oklahoma |url=https://shareok.org/bitstream/handle/11244/4115/7615823.PDF |access-date=2021-11-04}}</ref> [[Bill Mensch]] was one of the engineers who had actually designed the 5065 at Motorola for Olivetti.{{cn|date=March 2024}}

=== MK3870 ===
[[File:MK38P70 and MBM2716.jpg|thumb|Mostek MK38P70 [[piggyback microcontroller]] variant of the MK3870]]
A more popular product was the MK3870, which combined the two-chip [[Fairchild F8]] (3850 + 3851) into a single chip,<ref>{{cite web|access-date=2024-02-16 |date=2022-12-12 |title=A History of Early Microcontrollers, Part 6: The Fairchild F8 and Mostek MK3870 |publisher=eejournal.com |url=https://www.eejournal.com/article/a-history-of-early-microcontrollers-part-6-the-fairchild-f8-and-mostek-mk3870/}}</ref> introduced in 1977. William Bradley designed a host of custom products based on the 3870. Fairchild later licensed the 3870 back from Mostek. Mostek also produced [[Read-only memory|ROM]] chips on demand, as well as the chips powering the [[Hammond organ|Hammond electronic organ]].

=== MK3880===
{{multiple image |total_width = 230 |perrow = 1/2
| footer   = Mostek MK3880 (Zilog Z80) die
| image1   = KL Mostek MK3880P Z80.jpg
| caption1 = Mostek MK3880P (Zilog Z80)
| image2   = Mostek MK3880 top metal.jpg
| alt2     = Mostek MK3880 with metal
| caption2 = – metal layer
| image3   = Mostek MK3880 top metal removed.jpg
| alt3     = Mostek MK3880 without metal
| caption3 = – silicon only}}
During the introduction of the [[Zilog Z80|Z80]], [[Zilog]] needed a production partner while they got their own fabs set up. They first signed a production agreement with [[Synertek]], but the company later demanded they sign a [[second source]] deal, allowing Synertek to produce and sell the design on their own. Zilog refused, so the agreement was broken. Zilog then selected Mostek as the only other company capable of building a +5V device (as opposed to +5 and +12).{{sfn|Slater|2007|p=7}} Mostek had developed advanced layout methods which were applied to the Z80, resulting in the device being shrunk by 20%.{{sfn|Slater|2007|p=11}} Mostek was able to sign a [[second source]] deal for what it called the MK3880.{{sfn|Slater|2007|p=4}} The Z80 eventually became the most popular microcomputer family, and was used in millions of embedded devices as well as in many [[home computer]]s and computers using the de facto standard [[CP/M]] operating system, such as the [[Osborne 1|Osborne]], [[Kaypro]], and [[TRS-80]] models.{{efn|Older note left in: Mostek supposedly discovered that Zilog had modified the recipe for Z80 chips to keep the yields low{{Citation needed|date=January 2022}}, thereby buying Zilog time to build their own fabs.}}

=== Others ===
Mostek sought new microprocessor partners and negotiated deals with Intel to gain second sourcing rights to the [[Intel 8086]] microprocessor family and future x86 designs and with Motorola for rights to the [[Motorola 68000]] and [[VMEbus|VME]]. Mostek thus secured rights to every microprocessor family that would be important for the next 25 years. The Intel x86 microprocessors would go on to become the brains for the [[IBM PC]], while the Motorola 68000 would become the heart of the [[Macintosh|Apple Macintosh]] line. However, as with its telecom business, Mostek chose not to aggressively follow-up its entry into microprocessors—instead increasing its concentration on DRAMs.