General Instrument CP1600
Encyclopedia
The CP1600 was a 16-bit
microprocessor
created in a partnership between General Instrument
and Honeywell
in the 1970s. The CP1600's design was based on the PDP-11
, whose design also formed the basis of the Western Digital
MCP-1600
and influenced others. Honeywell
used the CP1600 in a number of process control computer
s and related systems, but its most widespread use was the CP1610 version in the Intellivision
video game console
.
closely followed the PDP-11's, but was not entirely compatible. The instruction opcode was only 10 bits, with the remaining 6 marked "Reserved for future expansion". It appears that the extra 6 bits were intended to be used with co-processors, asserting the PCIT line which stalled the CPU until released. Instructions might be one to three words long depending on the addressing format being used. Unlike similar CPUs, the CP1600 did not support memory-memory indirect addressing (offsets), and looping was implemented in a different way which allowed it to run much faster.
Like the PDP-11, the CP1600 used eight 16-bit "general purpose" processor register
s, although they were not truly general purpose as in modern designs. Only R0 was truly general purpose and has been described as "the primary accumulator". R1 through R3 were data counters, generally used for register-based addressing ("implied addressing"). R4 and R5 auto-incremented after being accessed, which made them useful for looping over collections of data.
R6 was the stack pointer, R7 the program counter. Since both of these registers were visible to the programmer, they could be used to implement multiple stacks, or support more complex branching, among other things. There were no implicit stack instructions; when R6 was used in a "read" operation it decremented the address and then returned the data being pointed at, simulating a
Like the PDP-11, one of the CP1600's notable features was the use of memory-mapped I/O
, meaning that devices were controlled by writing to certain locations in memory. Unlike the PDP-11's Unibus
, however, the CP1600 multiplexed its data and address lines in order to reduce pin count and fit into a 40-pin DIP
. This change meant that implementations had to use latches or buffers to be able to interface with the CPU as it changed the bus from indicating an address to data. This negatively affected I/O performance, and to address this problem GI designed the "Programmable Interface Controller"
which was designed to work in concert with the CP1600 as a channel controller.
The CP1600 was implemented in nMOS
and required +12, +5, -3 V power supplies; most internal logic was implemented in TTL (5 V). It had a 3.3 MHz clock (300 ns cycle time) that was later bumped to 5 MHz clock (200 ns cycle time), instructions executed within 1.6 and 4.8 microseconds. GI also produced a development system for the CP1600, the "GIMINI".
The CP1610, used in the Intellivision, was essentially a "de-tuned" CP1600 with several simplifications. In the Intellivision, the CP1610 ran at 894 kHz to match NTSC
signals, or 1 MHz for PAL
/SECAM
versions. Although users of the CP1600 in the traditional computer role were relatively rare, over 3 million Intellivisions were produced from 1980 until the video game crash of 1983
led to the closing of the Intellivision production lines in 1984.
Production of the CP1600 ended in 1985 when General Instruments spun off its microelectronics division to create Microchip Technology
. By this point a number of 32-bit designs like the MC68000 were available that limited interest in a 16-bit design like the CP1600, and their main existing customer, the Intellivision, was no longer in production. Many other products were also end-of-lifed at the same time, and their primary product was the PIC.
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...
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...
created in a partnership between General Instrument
General Instrument
General Instrument was an electronics manufacturer based in Horsham, PA specializing in semiconductors and cable television equipment. The company was active until 1997, when it split into which was later acquired by Vishay Intertechnology in 2001, CommScope and NextLevel Systems General...
and Honeywell
Honeywell
Honeywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....
in the 1970s. The CP1600's design was based on the PDP-11
PDP-11
The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years...
, whose design also formed the basis of the Western Digital
Western Digital
Western Digital Corporation is one of the largest computer hard disk drive manufacturers in the world. It has a long history in the electronics industry as an integrated circuit maker and a storage products company. Western Digital was founded on April 23, 1970 by Alvin B...
MCP-1600
MCP-1600
The MCP-1600 was a multi-chip microprocessor made by Western Digital in the late 1970s through the early 1980s. Used in the Pascal MicroEngine, the original AlphaMicro system, and the DEC LSI-11 microcomputer, a cost-reduced and compact implementation of the DEC PDP-11.There were three types of...
and influenced others. Honeywell
Honeywell
Honeywell International, Inc. is a major conglomerate company that produces a variety of consumer products, engineering services, and aerospace systems for a wide variety of customers, from private consumers to major corporations and governments....
used the CP1600 in a number of process control computer
Industrial Control Systems
Industrial control system is a general term that encompasses several types of control systems used in industrial production, including supervisory control and data acquisition systems, distributed control systems , and other smaller control system configurations such as skid-mounted programmable...
s and related systems, but its most widespread use was the CP1610 version in the Intellivision
Intellivision
The Intellivision is a video game console released by Mattel in 1979. Development of the console began in 1978, less than a year after the introduction of its main competitor, the Atari 2600. The word intellivision is a portmanteau of "intelligent television"...
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...
.
Description
The CP1600's instruction setInstruction set
An instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
closely followed the PDP-11's, but was not entirely compatible. The instruction opcode was only 10 bits, with the remaining 6 marked "Reserved for future expansion". It appears that the extra 6 bits were intended to be used with co-processors, asserting the PCIT line which stalled the CPU until released. Instructions might be one to three words long depending on the addressing format being used. Unlike similar CPUs, the CP1600 did not support memory-memory indirect addressing (offsets), and looping was implemented in a different way which allowed it to run much faster.
Like the PDP-11, the CP1600 used eight 16-bit "general purpose" processor register
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...
s, although they were not truly general purpose as in modern designs. Only R0 was truly general purpose and has been described as "the primary accumulator". R1 through R3 were data counters, generally used for register-based addressing ("implied addressing"). R4 and R5 auto-incremented after being accessed, which made them useful for looping over collections of data.
R6 was the stack pointer, R7 the program counter. Since both of these registers were visible to the programmer, they could be used to implement multiple stacks, or support more complex branching, among other things. There were no implicit stack instructions; when R6 was used in a "read" operation it decremented the address and then returned the data being pointed at, simulating a
POP, and when it was used in a "write" it would post-increment (like R4/R5) and write, like a PUSH.Like the PDP-11, one of the CP1600's notable features was the use of memory-mapped I/O
Memory-mapped I/O
Memory-mapped I/O and port I/O are two complementary methods of performing input/output between the CPU and peripheral devices in a computer...
, meaning that devices were controlled by writing to certain locations in memory. Unlike the PDP-11's Unibus
Unibus
The Unibus was the earliest of several computer bus technologies used with PDP-11 and early VAX systems manufactured by the Digital Equipment Corporation of Maynard, Massachusetts.-History:...
, however, the CP1600 multiplexed its data and address lines in order to reduce pin count and fit into a 40-pin DIP
Dual in-line package
In microelectronics, a dual in-line package is an electronic device package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board or inserted in a socket.A DIP is usually referred to as a DIPn, where n is...
. This change meant that implementations had to use latches or buffers to be able to interface with the CPU as it changed the bus from indicating an address to data. This negatively affected I/O performance, and to address this problem GI designed the "Programmable Interface Controller"
PIC microcontroller
PIC is a family of Harvard architecture microcontrollers made by Microchip Technology, derived from the PIC1650 originally developed by General Instrument's Microelectronics Division...
which was designed to work in concert with the CP1600 as a channel controller.
The CP1600 was implemented in nMOS
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
and required +12, +5, -3 V power supplies; most internal logic was implemented in TTL (5 V). It had a 3.3 MHz clock (300 ns cycle time) that was later bumped to 5 MHz clock (200 ns cycle time), instructions executed within 1.6 and 4.8 microseconds. GI also produced a development system for the CP1600, the "GIMINI".
Uses
NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
signals, or 1 MHz for PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
/SECAM
SECAM
SECAM, also written SÉCAM , is an analog color television system first used in France....
versions. Although users of the CP1600 in the traditional computer role were relatively rare, over 3 million Intellivisions were produced from 1980 until the video game crash of 1983
Video game crash of 1983
The North American video game crash was a serious event that brought an abrupt end to what is considered the second generation of console video gaming in North America. Beginning in 1983, the crash almost destroyed the then-fledgling industry and led to the bankruptcy of several companies producing...
led to the closing of the Intellivision production lines in 1984.
Production of the CP1600 ended in 1985 when General Instruments spun off its microelectronics division to create Microchip Technology
Microchip Technology
Microchip Technology is an American manufacturer of microcontroller, memory and analog semiconductors. Its products include microcontrollers , Serial EEPROM devices, Serial SRAM devices, KEELOQ devices, radio frequency devices, thermal, power and battery management analog devices, as well as...
. By this point a number of 32-bit designs like the MC68000 were available that limited interest in a 16-bit design like the CP1600, and their main existing customer, the Intellivision, was no longer in production. Many other products were also end-of-lifed at the same time, and their primary product was the PIC.
External links
- "CP1610" at the Intellivision Wiki