Control unit

The control unit (CU) is a component of a computer's central processing unit (CPU) that directs the operation of the processor.

Traditionally, the term "CPU" refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry.

John von Neumann included the control unit as part of the von Neumann architecture.

On some processors, the Control Unit may be further broken down into additional units, such as an instruction unit or scheduling unit to handle scheduling, or a retirement unit to deal with results coming from the instruction pipeline.

It is a part of the control unit, which in turn is part of the CPU.

The CU is normally the first CPU unit to accept from an externally stored computer program a single instruction (based on the CPU's instruction set).

There are two basic ways to build a control unit to implement this description (although many designs use middle ways or compromises):

John von Neumann included the control unit as part of the von Neumann architecture.

The CU receives external instructions or commands which it converts into a sequence of control signals that the CU applies to the data path to implement a sequence of register-transfer level operations.

This results in a computer that could run a complete program and require no human intervention to make hardware changes between instructions (as had to be done when using only punch cards for computations before stored programmed computers with CUs were invented).

On some processors, the Control Unit may be further broken down into additional units, such as an instruction unit or scheduling unit to handle scheduling, or a retirement unit to deal with results coming from the instruction pipeline.

Hardwired control units are implemented through use of combinational logic units, featuring a finite number of gates that can generate specific results based on the instructions that were used to invoke those responses.

This architecture is preferred in reduced instruction set computers (RISC) as they use a simpler instruction set.

The algorithm for the microprogram control unit, unlike the hardwired control unit, is usually specified by flowchart description.

Digital Imaging Integrated Circuit (often styled as "DiG!C") is Canon Inc.'s name for a family of signal processing and control units for digital cameras and camcorders.

Microcode is used in general-purpose central processing units, although in current desktop CPUs it is only a fallback path for cases that the faster hardwired control unit cannot handle.

A control store is the part of a CPU's control unit that stores the CPU's microprogram.

This distinction was extended in the Von Neumann architecture, where the CPU consists of two main parts: The control unit and the arithmetic logic unit (ALU).

They were constructed with bipolar devices, in a bit-slice topology, and were designed to be used as modular components each representing a different aspect of a computer control unit (CCU).

Control unit contains a program counter and instruction registers.

Since MikroSim operability starts on the basis of microcode development, defined as a sequence of micro instructions (microcoding) for a virtual control unit, the software's intention is on first approach a microcode simulator with various levels of abstractions including the ability of CPU simulators and instruction set emulators.

Unlike almost all later consoles, these systems were typically not computers (in which a CPU is running a piece of software), but contained a hardwired game logic.

This describes a design architecture for an electronic digital computer with subdivisions of a processing unit consisting of an arithmetic logic unit and processor registers, a control unit containing an instruction register and program counter, a memory to store both data and instructions, external mass storage, and input and output mechanisms.

It consists of a very simple control unit that runs microcode from a 512-words store.