FACTOID # 19: Cheap sloppy joes: Looking for reduced-price lunches for schoolchildren? Head for Oklahoma!
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Control unit

A control unit is the part of a CPU or other device that directs its operation. The outputs of the unit control the activity of the rest of the device. A control unit can be thought of as a finite state machine. Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ... Fig. ...


At one time control units for CPUs were ad-hoc logic, and they were difficult to design. Now they are often implemented as a microprogram that is stored in a control store. Words of the microprogram are selected by a microsequencer and the bits from those words directly control the different parts of the device, including the registers, arithmetic and logic units, instruction registers, buses, and off-chip input/output. In modern computers, each of these subsystems may have its own subsidiary controller, with the control unit acting as a supervisor. (See also CPU design and computer architecture.) A microprogram implements a CPU instruction set. ... A control store is the part of a CPUs control unit that stores the CPUs microprogram. ... In the field of computer architecture and engineering, a sequencer or microsequencer, is a part of a control unit of a CPU. It generates the addresses used to step through the microprogram of a control store. ... In computer architecture, a processor register is a small amount of very fast computer memory used to speed the execution of computer programs by providing quick access to commonly used values—typically, the values being in the midst of a calculation at a given point in time. ... ALU redirects here. ... In computing, an instruction register is the part of a CPUs control unit that stores the instruction currently being executed. ... In computer architecture, a bus is a subsystem that transfers data or power between computer components inside a computer or between computers and typically is controlled by device driver software. ... In computing, input/output, or I/O, is the collection of interfaces that different functional units (sub-systems) of an information processing system use to communicate with each other, or the signals (information) sent through those interfaces. ... CPU design is the hardware design of a central processing unit. ... A typical vision of a computer architecture as a series of abstraction layers: hardware, firmware, assembler, kernel, operating system and applications (see also Tanenbaum 79). ...


The control unit is the circuitry that controls the flow of information through the processor, and coordinates the activities of the other units within it. In a way, it is the "brain within the brain", as it controls what happens inside the processor, which in turn controls the rest of the PC.


The functions performed by the control unit vary greatly by the internal architecture of the CPU, since the control unit really implements this architecture. On a regular processor that executes x86 instructions natively, the control unit performs the tasks of fetching, decoding, managing execution and then storing results. On a processor with a RISC core the control unit has significantly more work to do. It manages the translation of x86 instructions to RISC micro-instructions, manages scheduling the micro-instructions between the various execution units, and juggles the output from these units to make sure they end up where they are supposed to go. On one of these processors the control unit may be broken into other units (such as a scheduling unit to handle scheduling and a retirement unit to deal with results coming from the pipeline) due to the complexity of the job it must perform.


  Results from FactBites:
 
Control unit - Wikipedia, the free encyclopedia (230 words)
A control unit is the part of a CPU or other device that directs its operation.
The outputs of the unit control the activity of the rest of the device.
Words of the microprogram are selected by a microsequencer and the bits from those words directly control the different parts of the device, including the registers, arithmetic and logic units, instruction registers, buses, and off-chip input/output.
Engine Control Unit - Wikipedia, the free encyclopedia (1477 words)
This kind of electronic control is less common in piston-engined aeroplanes than in automobiles, because of the large costs of certifying parts for aviation use, relatively small demand, and the consequent stagnation of technological innovation in this market.
Gear control : Tells the ECU to cut ignition during (sequential gearbox) upshifts or blip the throttle during downshifts.
They generally do not have the ability to control extra ancilliary devices, such as variable valve timing if the factory vehicle was a fixed geometry camshaft or boost control if the factory car was not turbocharged.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m