The Signetics 2650, was a very early (1975) 8-bit

8-bit

The first widely adopted 8-bit microprocessor was the Intel 8080, being used in many hobbyist computers of the late 1970s and early 1980s, often running the CP/M operating system. The Zilog Z80 and the Motorola 6800 were also used in similar computers...

 microprocessor

Microprocessor

A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...

. According to Adam Osborne

Adam Osborne

Adam Osborne was an American author, book and software publisher, and computer designer who founded several companies in the United States and elsewhere.- Computers :...

's classic book An Introduction to Microprocessors Vol 2: Some Real Products, it was "the most 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...

-like" of the microprocessors available at the time.

Signetics

Signetics

Signetics, once a major player in semiconductor manufacturing, made a variety of devices which included integrated circuits, bipolar and MOS, the Dolby circuit, logic, memory and analog circuits. They developed microprocessors like the 2650, the bipolar 8X300 and had licensed Motorola 68000...

 sold development boards e.g. the PC1500 "Adaptable Board Computer", ranging in price from $AUD 165 to $AUD 400. The chip by itself sold for around $AUD 20. Several hardware construction projects and programming articles were published in magazines such as Electronics Australia and Elektor and related kits were sold by electronics stores. These factors led to its use by a number of hobbyists, particularly in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

 where a user group was formed.

The chip contained 7 8-bit general purpose registers

Processor register

In computer architecture, a processor register is a small amount of storage available as part of a CPU or other digital processor. Such registers are addressed by mechanisms other than main memory and can be accessed more quickly...

, although only 4 were visible at any time. It was limited to a 15-bit address space

Address space

In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity.- Overview :...

 (thereby addressing a maximum of 32KB of memory), since the upper bit of a 16-bit memory reference was reserved to indicate that the indirect memory addressing mode

Addressing mode

Addressing modes are an aspect of the instruction set architecture in most central processing unit designs. The various addressing modes that are defined in a given instruction set architecture define how machine language instructions in that architecture identify the operand of each instruction...

 was to be used (a 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...

-like feature).

While there were nine different addressing mode

Addressing mode

Addressing modes are an aspect of the instruction set architecture in most central processing unit designs. The various addressing modes that are defined in a given instruction set architecture define how machine language instructions in that architecture identify the operand of each instruction...

s, the lack of any 16-bit

16-bit

-16-bit architecture:The HP BPC, introduced in 1975, was the world's first 16-bit microprocessor. Prominent 16-bit processors include the PDP-11, Intel 8086, Intel 80286 and the WDC 65C816. The Intel 8088 was program-compatible with the Intel 8086, and was 16-bit in that its registers were 16...

 registers and the 15-bit address space prevented widespread use. Despite this, an operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 ("2650 DOS") was available, along with a BASIC interpreter, and many games of the Hunt the Wumpus

Hunt the Wumpus

Hunt the Wumpus is an early computer game, based on a simple hide and seek format featuring a mysterious monster that lurks deep inside a network of rooms. It was originally a text-based game written in BASIC...

 style. Most programs were written in assembly language

Assembly language

An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...

.

Two types of video game console

Video game console

A video game console is an interactive entertainment computer or customized computer system that produces a video display signal which can be used with a display device to display a video game...

 used the Signetics 2650 or 2650A. The first group of consoles are based on the video display controller

Video Display Controller

A Video Display Controller or VDC is an integrated circuit which is the main component in a video signal generator, a device responsible for the production of a TV video signal in a computing or game system...

 2636 Programmable Video Interface; the 1292 Advanced Programmable Video System

1292 Advanced Programmable Video System

The 1292 Advanced Programmable Video System is a video game console released by European company Radofin in 1976. It is part of a group of software-compatible consoles which include the Interton VC-4000 and the Voltmace Database...

 and the closely related Interton VC4000

VC 4000

The VC 4000 is an early 8-bit cartridge-based game console released in Germany in 1978 by Interton. The console is quite obscure outside Germany, but many software compatible systems can be found in many European countries...

 belong to this group. Those were released in Germany in 1976 and 1978 respectively. The second group of consoles were based on the Signetics 2637 as a video display controller

Video Display Controller

A Video Display Controller or VDC is an integrated circuit which is the main component in a video signal generator, a device responsible for the production of a TV video signal in a computing or game system...

; Emerson Arcadia 2001

Arcadia 2001

The Arcadia 2001 is a second-generation 8-bit console released by Emerson Radio Corp. The game library was composed of 51 unique games and about 10 variations. The graphic quality is similar to that of the Intellivision and the Odyssey²....

 which was released in 1982 and which used a Signetics 2650 running at 3.58 MHz as a CPU

Central processing unit

The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

 belong to this group together with many other ones software-compatible (Leonardo, Hanimex MPT-03 etc.).

The processor was also used in the Signetics Instructor 50, which was a small computer designed to teach the use and programming of the Signetics 2650 CPU.

Second sources

In 1975 Signetics was sold to Philips

Philips

Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....

 and the 2650 was later incorporated into the Philips Semiconductors line. They made a version of the 2650 called the MAB2650A.

The most well known licensed copy of the Signetics/Philips 2650 was the 2650-P-02 from Synertek

Synertek

Synertek, Inc. was an American semiconductor manufacturer founded in 1973. The initial founding group consisted of Bob Schreiner , Dan Floyd, Zvi Grinfas, Jack Balletto, and Gunnar Wetlesen. The manufacturing technology was MOS/LSI...

.

Other producers of licensed copies of the chip were Harris

Harris Corporation

Harris Corporation is a Florida-based international communications equipment company that produces wireless equipment, electronic systems, and both terrestrial and spaceborne antennas for use in the government, defense, and commercial sectors. It is also the largest private-sector employer in...

 and Intersil

Intersil

Intersil Corporation is an American company that specializes in the design, development and manufacturing of high-performance analog semiconductors for four high-growth markets — Communications, Computing, High End Consumer and Industrial.-Company history:...

.

Peripheral Chips

The 2650 came with a full complement of peripheral chips:

• 2621 Video Encoder (PAL)
• 2622 Video Encoder (NTSC)
• 2636 Programmable Video Interface
• 2637 Universal Video Interface
• 2651 Programmable Communication Interface
• 2652 Multi-Protocol Communications Circuit (incl. Synchronous Data Link Control (SDLC))
• 2653 Polynomial Generator / Checker
• 2655 Programmable Peripheral Interface
• 2657 Direct Memory Access
• 2656 System Memory Interface
• 2661 Programmable Communication Interface
• 2670 Display Character and Graphics Generator
• 2671 Programmable Keyboard and Communications Controller
• 2672 Programmable Video Timing Controller
• 2673 Video Attributes Controller

Many of these peripheral chips were designed so they could also be used with other microprocessor, for example the datasheet of the 2672 suggests using it with an Intel 8048

Intel 8048

The MCS-48 microcontroller series, Intel's first microcontroller, was originally released in 1976. Its first members were 8048, 8035 and 8748....

 microcontroller

Microcontroller

A microcontroller is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM...

.

Descendants of the 2651/2661 serial communications chips are still sold as the Philips SC26 series.

External links

• Datasheet
• Signetics 2650 family CPU World
• Instructor 50 Old-computers.com
• Adaptable Board Computer development system complete with 1 KiB PipBug monitor
  Machine code monitor
  A machine code monitor is software built into or separately available for various computers, allowing the user to enter commands to view and change memory locations on the machine, with options to load and save memory contents from/to secondary storage.Machine code monitors became something of a...
  
   and 512 bytes of RAM
  Ram
  -Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
  
  
• the 2650 at www.cpu-museum.com
• Electronics Australia 2650 board at yesterdaystechnology.com
• Ami/WinArcadia emulates various 2650-based machines including the Signetics Instructor 50
• Emerson Arcadia 2001 Central the world's largest site for 2650-based machines