Rekursiv
Encyclopedia
Rekursiv was a computer processor designed by David M. Harland
David M. Harland
David M. Harland is an author and space historian whose books in recent years include How NASA Learned to Fly in Space, Exploring the Moon - The Apollo Expeditions, and The Story of the Space Shuttle and The Story of Space Station Mir...

 in the mid-1980s for Linn Smart Computing in Glasgow
Glasgow
Glasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...

, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

. It was one of the few computer architecture
Computer architecture
In computer science and engineering, computer architecture is the practical art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals and the formal modelling of those systems....

s intended to implement object-oriented concepts directly in hardware. The Rekursiv operated directly on objects rather than bits, nibbles, bytes and words. Virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...

 was used as a persistent object store and unusually, the processor instruction set supported recursion
Recursion
Recursion is the process of repeating items in a self-similar way. For instance, when the surfaces of two mirrors are exactly parallel with each other the nested images that occur are a form of infinite recursion. The term has a variety of meanings specific to a variety of disciplines ranging from...

 (hence the name).

The project originated in an initiative within the hi-fi manufacturer Linn Products
Linn Products
Linn Products is a Scottish company, based in Glasgow, that manufactures hi-fi audio equipment, home theatre, and multi-room integrated audio systems...

 to improve its manufacturing automation systems, which at the time ran on a DEC VAX minicomputer
Minicomputer
A minicomputer is a class of multi-user computers that lies in the middle range of the computing spectrum, in between the largest multi-user systems and the smallest single-user systems...

. This resulted in the design of Lingo, an object-oriented programming language
Object-oriented programming language
This is a list of object-oriented programming programming languages.-Languages with object-oriented features:*ABAP*Ada 95*AmigaE*BETA*Blue*Boo*C++*C#*COBOL*Cobra*ColdFusion*Common Lisp*COOL*CorbaScript*Clarion*CLU*Curl*D*Dylan*E*Eiffel...

 derived from Smalltalk
Smalltalk
Smalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the "new world" of computing exemplified by "human–computer symbiosis." It was designed and created in part for educational use, more so for constructionist...

 and ALGOL
ALGOL
ALGOL is a family of imperative computer programming languages originally developed in the mid 1950s which greatly influenced many other languages and became the de facto way algorithms were described in textbooks and academic works for almost the next 30 years...

. Due to the poor performance of Lingo on the VAX, a subsidiary company, Linn Smart Computing Ltd., was formed to develop a new processor to efficiently run Lingo.

The Rekursiv processor consisted of four gate-array chips named Numerik (32-bit
32-bit
The range of integer values that can be stored in 32 bits is 0 through 4,294,967,295. Hence, a processor with 32-bit memory addresses can directly access 4 GB of byte-addressable memory....

 ALU
Arithmetic logic unit
In computing, an arithmetic logic unit is a digital circuit that performs arithmetic and logical operations.The ALU is a fundamental building block of the central processing unit of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers...

), Logik (instruction sequencer), Objekt (object-oriented memory management unit
Memory management unit
A memory management unit , sometimes called paged memory management unit , is a computer hardware component responsible for handling accesses to memory requested by the CPU...

) and Klock (processor clock and support logic). A small number of prototype VMEbus
VMEbus
VMEbus is a computer bus standard, originally developed for the Motorola 68000 line of CPUs, but later widely used for many applications and standardized by the IEC as ANSI/IEEE 1014-1987. It is physically based on Eurocard sizes, mechanicals and connectors , but uses its own signalling system,...

 boards, called Hades, comprising these four chips plus 80 MB of RAM were produced. These were intended for installation in a host system such as a Sun-3
Sun-3
Sun-3 was the name given to a series of UNIX computer workstations and servers produced by Sun Microsystems, launched on September 9th, 1985. The Sun-3 series were VMEbus-based systems similar to some of the earlier Sun-2 series, but using the Motorola 68020 microprocessor, in combination with the...

 workstation
Workstation
A workstation is a high-end microcomputer designed for technical or scientific applications. Intended primarily to be used by one person at a time, they are commonly connected to a local area network and run multi-user operating systems...

.

Although the Rekursiv was never fully developed and was not a commercial success, several Hades boards were used in academic research projects in the UK. The last known copy of a Rekursiv computer ended up at the bottom of the Forth and Clyde canal
Forth and Clyde Canal
The Forth and Clyde Canal crosses Scotland, providing a route for sea-going vessels between the Firth of Forth and the Firth of Clyde at the narrowest part of the Scottish Lowlands. The canal is 35 miles long and its eastern end is connected to the River Forth by a short stretch of the River...

in Glasgow.
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