Mostek Calculator Integrated Circuits

MOSTEK.jpg (105775 Byte)Mostek Corporation was founded in 1969 as a spin-off of Texas Instruments and engaged in the manufacturing and marketing of Metal Oxide Semiconductors and Large Scale Integration (MOS/LSI) integrated circuits. Already in May, 1970 Mostek started the development of the MK6010, the world's first "single-chip" calculator circuit for for Nippon Calculating Machine Company, better known under the brand Busicom. The MK6010 introduced January, 1971 - was used in Busicom's first handheld model, the Handy LE-120. Sold in 1971, it was the world's smallest handheld calculator for at least a year. 

Texas Instruments announced the
"TMS1802 calculator-on-a-chip" in September 17, 1971, about a year later Mostek introduced the MK5020P, an improved but pin-compatible calculator chip. Not only did Mostek attract the attention of the electronic community, but they also attracted the attention of major consumers of MOS circuits and the company began an important relationship with Hewlett-Packard as the major supplier of integrated circuits for HP's scientific calculators. Hewlett-Packard soon became Mostek's largest customer. In addition, Mostek's memory production was on the way to making it the worlds leading RAM supplier.

Find a list of all known Texas Instruments calculator chips here.

MOSTEK_TEAM.jpg (174626 Byte)The number system of Mostek gives immediately an idea if a calculator chip was a custom design (MK6***) or a commercial device (MK5***):

MK1 - First product: A 256 bit shift register
MK3 - Some ROM but mostly CPU like MK3870 F8 series
MK4 - Memory
MK5 - Telecom, industrial, calculator, clocks, DATACOM
MK6 - Customized parts
MK7 - CPU Cards

Thank you to Jim Garrett and Frank Boehm!


First "single chip" calulator

These chips are manufactured in a high-threshold, p-channel MOS process and using Dual-Inline-Ceramic (CDIP) packages with 40 pins.
The MK6010 did not include keyboard encoding, keyboard debouncing, clock generator or the display drivers. It operates from unusual voltages of -12V and -24V.

Type Year Function Calculator Comments
MK6010 1971 Basic Busicom Junior, 120-DN First "single chip" calculator, outdates TMS1802
Four functions, 10 digits
MK6010L 1971 Basic Busicom LE-120A Differences to MK6010 not yet discovered
1972 Basic Busicom Exec 121-DK Chip set, Memory, 12 digits
MK5010P 1972 Basic Rapidman 800 Identical device with the MK6010.
Once design cleared customer hold time restriction then allowed to sell on open market
MK5012P 1972 Basic Neckermann electronic dc8 12-digit version of the MK5010P
1972 Desktop Master Calculator Master II, Commodore US-121P R1200 Chip set, Memory, Constant, 5/4 Rounding, 12 digits
MK5015P 1972 Desktop Printing Commodore US-121P, Hunor 126 Interface to Seiko 102 Two-color Impact Printer for MK5013P, MK5014P

Early BASIC calculator chips

These chips are manufactured in an ion-implantation, depletion-mode load, P-channel MOS process and using Dual-Inline-Ceramic (CDIP) packages with 28 pins.

Type Year Function Calculator Comments
MK5020A 1973 Basic Corvus 0310, 
Heathkit IC-2006
[+=],[-=] or [+],[-],[=] keys, sqr(x), %, 8 digits
MK5020B 1973 Basic Aristo M64,
Privileg 01466
[+=],[-=] or [+],[-],[=] keys, sqr(x), %, 8 digits
MK5021C 1973 Basic    [+=],[-=] or [+],[-],[=] keys, sqr(x), %, 10 digits

Later BASIC calculator chips

Enhanced chips with partly integrated display drivers and more functions and using Dual-Inline-Ceramic (CDIP) or Plastic (DIP) packages with 28 pins. 

Type Year Function Calculator Comments
MK6092P, MK5017 1973 Basic + Clock Corvus 305 Sqr(x), 1/x, %, 10 digits
Clock with date
MS5020A 1974 Basic Corvus 310 Constant, sqr(x), %, 8 digits
MK5020AN 1974 Basic Corvus 312 Constant, sqr(x), %, 8 digits
Different to MK5020A introduced in 1973!
MK5020BN 1974 Basic Aristo M64 Constant, sqr(x), %, 8 digits
Different to MK5020A introduced in 1973!
MK5021BN 1974 Basic Corvus 300E Sqr(x), 1/x, %, 10 digits
MS5021CN 1973 Basic Vanguard X1010 Constant, sqr(x), %, 10 digits
MK5022AN 1974 Basic Corvus 322 Memory, %, 8 digits
MK50201K 1974 Basic Panasonic JE-2001U Memory, %, 8 digits
MK50203N 1974 Basic Corvus 415, 307 Memory, Constant, 1/x, %, 8 digits
MK50220N 1974 Basic Olympia CD72 Unknown specifications
MK50280AN 1974 Basic Corvus 400 (early) Counter, %, 8 digits
MK50281N 1974 Basic Melcor 392 Memory, Constant, %, 8 digits 
MK50282N, MK50282AN 1974 Basic Corvus 400 (late) Counter, Constant, %, 8 digits
MK50283N 1974 Basic   Constant, sqr(x), %, 8 digits 
MK50310N 1974 Basic Corvus 411 Memory, sqr(x), 1/x, Pi, 8 digits
MK50311N 1974 Basic Corvus 625 (First design) Memory, sqr(x), 1/x, x2, 8 digits
MK50312AN 1974 Basic Corvus 615, Corvus 625 (Second design) Memory, sqr(x), 8 digits VFD-display
MK50321N 1974 Basic APF Mark 41 Unknown specifications
MK6225N 1975 Checkbook Corvus 525 CheckMaster Memory, 6 digits
MK50112N 1975 Basic Corvus 804 Memory, sqr(x), %, 8 digits

Chip set for scientific and financial calculators

With the MK50075 Mostek created a novel architecture for scientific and financial calculators using external ROM circuits (read only memory). 

Type Year Function Calculator Comments
MK50075 1975 Data processor (RALU) Corvus 500, Corvus 600 Needs minimum 1 external ROM, expandable to 16 ROMs
BCD/HEX ALU, 4 15-digit Registers, Digit and Segment outputs, 14 digits
MK50101 1975 Financial Corvus 600 ROM#1 (1k Words ROM, 7 15-digit Registers)
MK50102 1975 Financial Corvus 600 ROM#2 (1k Words ROM, 7 15-digit Registers)
MK50103 1975 Scientific Corvus 500 ROM#1 (1k Words ROM, 7 15-digit Registers)
MK50104 1975 Scientific Corvus 500 ROM#2 (1k Words ROM, 7 15-digit Registers)

Calculator chips manufactured for Hewlett-Packard

Custom specific designs. 

Type Year Function Calculator Comments
HP65-CPU 1973 Programmable Scientific HP-65 Hybrid CPU-module
MK6111 1973 ROM 1,024*10 bits HP-65 ROM#1
MK6112 1973 ROM 1,024*10 bits HP-65 ROM#2
MK6113 1973 ROM 1,024*10 bits HP-65 ROM#3
MK6020 1972 Arithmetic Chip HP-35, HP-45, HP-55, HP-70  
MK6021 1972 Control and Timing Chip HP-35  
MK6022 1972 ROM 256*10 bits HP-35 ROM#1
MK6023 1972 ROM 256*10 bits HP-35 ROM#2
MK6024 1972 ROM 256*10 bits HP-35 ROM#3
MK6036 1973 RAM 10*56 bits HP-45, HP-55, HP-70  
MK6134 1973 ROM 1024*10 bits HP-55   
MK6215 1974 Arithmetic Chip HP-22, HP-25, HP-25C   
MK6216 1974 Arithmetic Chip HP-29C, HP95C, HP-97   
MK6217 1974 Arithmetic Chip HP-21   
MK6220 1974 RAM 16*56 bits HP-22, HP-25  
MK6250 1975 Card Reader Control HP-67, HP-97   
MK60038 1975 ROM HP-67 added Anode drivers
MK60126 1975 ROM HP-25, HP-25C  
MK60142 1975 ROM HP-19C  
MK60171 1975 ROM/RAM HP-67, HP-97  
MK60172 1975 ROM/RAM HP-67, HP-97  
MK60175 1975 ROM/RAM HP-67  
MK60176 1975 ROM/RAM HP-67  
MK60185 1975 ROM/RAM HP-19C, HP-29C  

Thanks to Eric Smith.

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If you have additions to the above article please email:

Joerg Woerner, January 14, 2010. No reprints without written permission.