DATAMATH CALCULATOR MUSEUM

Mostek Calculator Integrated Circuits

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 Nippon Calculating Machine Company, better known under their brand Busicom. The MK6010 – introduced in 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 one year.

Texas Instruments announced the "TMS1802 calculator-on-a-chip" in September 17, 1971, about one 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 one of the leading 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 world's leading RAM supplier.

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

The numbering system of Mostek gives us immediately an idea if a calculator chip was a custom design (MK6***) or a commercial device (MK5***):

• MK1 - First product: 256-bit shift register
• MK2 - ROM, EPROM
• MK3 - Some ROM but mostly CPU like MK3870 F8 series
• MK4 - Memory
• MK5 - Telecom, industrial, calculators, clocks, DATACOM
• MK6 - Customized parts
• MK7 - CPU Cards

Thank you to Jim Garrett and Frank Boehm!

First "single chip" calculator circuit

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
MK6018, MK6019	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
MK5013P, MK5014P	1972	Desktop	Master Calculator Master II, Commodore US-121P	R1200 Chipset, 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, √x, %, 8 digits
MK5020B	1973	Basic	Aristo M64, Privileg 01466	[+=] [-=] or [+] [-] [=] keys, √x, %, 8 digits
MK5021C	1973	Basic		[+=] [-=] or [+] [-] [=] keys, √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	√x, 1/x, %, 10 digits Clock with date
MS5020A	1974	Basic	Corvus 310	Constant, √x, %, 8 digits
MK5020AN	1974	Basic	Corvus 312	Constant, √x, %, 8 digits Different to MK5020A introduced in 1973!
MK5020BN	1974	Basic	Aristo M64	Constant, √x, %, 8 digits Different to MK5020A introduced in 1973!
MK5021BN	1974	Basic	Corvus 300E	√x, 1/x, %, 10 digits
MS5021CN	1973	Basic	Vanguard X·1010	Constant, √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, √x, %, 8 digits
MK50310N	1974	Basic	Corvus 411	Memory, √x, 1/x, PI, 8 digits
MK50311N	1974	Basic	Corvus 625 (First design)	Memory, √x, 1/x, x², 8 digits
MK50312AN	1974	Basic	Corvus 615, Corvus 625 (Second design)	Memory, √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, √x, %, 8 digits

Chipset 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 manufactured by Hewlett-Packard
MK6111	1973	ROM 1,024*10 bits	HP-65	HP 1818-0073: ROM#1
MK6112	1973	ROM 1,024*10 bits	HP-65	HP 1818-0074: ROM#2
MK6113	1973	ROM 1,024*10 bits	HP-65	HP 1818-0075: ROM#3
MK6020	1972	Arithmetic and Register Chip	HP-35, HP-45, HP-55, HP-70	HP 1818-0011, HP 1820-1169
MK6021	1972	Control and Timing Chip	HP-35	HP 1818-0012, HP 1818-0078
MK6022	1972	ROM 256*10 bits	HP-35	HP 1818-0028: ROM#1
MK6023	1972	ROM 256*10 bits	HP-35	HP 1818-0024: ROM#2
MK6024	1972	ROM 256*10 bits	HP-35	HP 1818-0026: ROM#3
MK6036	1973	RAM 10*56 bits	HP-45, HP-55, HP-70	HP 1820-0993, HP 1820-1393
MK6111	1973	ROM 1,024*10 bits	HP-65	HP 1818-0073: ROM#1
MK6112	1973	ROM 1,024*10 bits	HP-65	HP 1818-0074: ROM#2
MK6113	1973	ROM 1,024*10 bits	HP-65	HP 1818-0075: ROM#3
MK6134	1974	ROM 1,024*10 bits	HP-55	HP 1818-0118
MK6215	1974	Arithmetic Chip	HP-21, HP-22, HP-25, HP-25C	HP 1820-1523
MK6216	1974	Arithmetic Chip	HP-21, HP-22, HP-25, HP-29C, HP-67, HP-91, HP-92, HP-95C, HP-97	HP 1820-1596
MK6217	1974	Arithmetic Chip	HP-21	HP 1820-1741
MK6218	1974	Arithmetic Chip	HP-67, HP-97	HP 1820-1812
MK6220	1974	RAM 16*56 bits	HP-22, HP-25, HP-91	HP 1820-1564
MK6250	1975	Card Reader Control	HP-67, HP-97	HP 1820-1751
MK60033	1975	ROM	HP-67	HP 1818-0227: Added Anode drivers - replaced by MK60038
MK60038	1975	ROM	HP-67	HP 1818-0268: Added Anode drivers
MK60040	1975	ROM	HP-92	HP 1818-0345: Added Anode drivers
MK60126	1975	ROM	HP-25, HP-25C	HP 1818-0154
MK60142	1975	ROM	HP-19C	HP 1818-0387
MK60171	1975	ROM/RAM	HP-67, HP-97	HP 1818-0228
MK60172	1975	ROM/RAM	HP-67, HP-97	HP 1818-0226
MK60175	1975	ROM/RAM	HP-67	HP 1818-0232
MK60176	1975	ROM/RAM	HP-67	HP 1818-0231
MK60181	1975	ROM/RAM	HP-92	HP 1818-0346
MK60182	1975	ROM/RAM	HP-92	HP 1818-0347
MK60183	1975	ROM/RAM	HP-92	HP 1818-0349
MK60184	1975	ROM/RAM	HP-92	HP 1818-0351
MK60185	1975	ROM/RAM	HP-19C, HP-29C	HP 1818-0379
MK62181	1975	PIK	HP-91	HP 1820-1680
MK62182	1975	PIK	HP-92	HP 1820-1896

Thanks to Eric Smith.

If you have additions to the above article please email: joerg@datamath.org.