The IMP-16, by

National Semiconductor National Semiconductor Corporation was an United States of America, American Semiconductor manufacturing, semiconductor manufacturer, which specialized in analogue electronics, analog devices and subsystems, formerly headquartered in Santa Clara, ...

, was the first multi-chip

16-bit 16-bit microcomputers are microcomputers that use 16-bit microprocessors. A 16-bit register can store 216 different values. The range of integer values that can be stored in 16 bits depends on the integer representation used. With the two ...

microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...

, released in 1973. It consisted of five PMOS

integrated circuits An integrated circuit (IC), also known as a microchip or simply chip, is a set of electronic circuits, consisting of various electronic components (such as transistors, resistors, and capacitors) and their interconnections. These components a ...

: four identical RALU chips, short for

register Register or registration may refer to: Arts, entertainment, and media Music * Register (music), the relative "height" or range of a note, melody, part, instrument, etc. * ''Register'', a 2017 album by Travis Miller * Registration (organ), ...

and ALU, providing the data path, and one CROM, Control and

ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...

, providing control sequencing and

microcode In processor design, microcode serves as an intermediary layer situated between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. It consists of a set of hardware-level instructions ...

storage. The IMP-16 is a bit-slice processor; each RALU chip provides a

4-bit 4-bit computing is the use of computer architectures in which integer (computer science), integers and other data (computer science), data units are 4 bits wide. 4-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures a ...

slice of the register and arithmetic that work in parallel to produce a 16-bit word length. Each RALU chip stores its own 4 bits of the program counter, several registers, the ALU, a 16-word LIFO stack, and status flags. There were four 16-bit accumulators, two of which could be used as index registers. The

instruction set architecture In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. A device or program that executes instructions described by that ISA, ...

was similar to that of the

Data General Nova The Nova is a series of 16-bit computing, 16-bit minicomputers released by the American company Data General. The Nova family was very popular in the 1970s and ultimately sold tens of thousands of units. The first model, known simply as "Nov ...

. The chip set could be extended with the CROM chip (IMP-16A / 522D) that implemented 16-bit multiply and divide routines. The chipset was driven by a two-phase 715 kHz non-overlapping clock that had a +5 to -12 voltage swing. An integral part of the architecture was a 16-bit input mux that provided various condition bits from the ALUs such as zero, carry, overflow along with general purpose inputs. The microprocessor was used in the IMP-16P microcomputer and Jacquard Systems' J100 but saw little other use. The IMP-16 was later superseded by the PACE and INS8900 single-chip 16-bit microprocessors, which had a similar architecture but were not binary compatible. It was also used in the Aston Martin Lagonda, thanks to National Semiconductor's chairman Peter Sprague being a major shareholder in

Aston Martin Aston Martin Lagonda Global Holdings PLC () is a British manufacturer of Luxury car, luxury sports cars and grand tourers. Its predecessor was founded in 1913 by Lionel Martin and Robert Bamford. Headed from 1947 by David Brown (entrepreneur ...

at the time.https://sprague.com/peter-sprague/aston-martin/

References

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External links

IMP-16C board at the Selectric Typewriter Museum

IMP-16 The IMP-16, by National Semiconductor, was the first multi-chip 16-bit computing, 16-bit microprocessor, released in 1973. It consisted of five PMOS logic, PMOS integrated circuits: four identical RALU chips, short for Processor register, regist ...

16-bit microprocessors Computers using bit-slice designs