there are a great many variations in architecture between the different
kinds of CPU, we shall begin my looking at a simplified model of the
structure. The model to be used can
be seen on the right
of this page, and is a good basis on which to build your knowledge of
the workings of a microprocessor. The simplified model consists of five
parts, which are:
|The simplified model of the central processing
unit. Click on an area for more details.
Arithmetic & Logic Unit (ALU)
The part of the central processing unit that deals with operations such
as addition, subtraction, and multiplication of integers and Boolean
operations. It receives control signals from the control unit telling
it to carry out these operations. For more, click the title above.
Control Unit (CU)
This controls the movement of instructions in and out of the processor,
and also controls the operation of the ALU. It consists of a decoder,
logic circuits, and a clock to ensure everything happens at the correct
time. It is also responsible for performing the instruction execution cycle.
More on the control unit can be discovered by clicking the title above.
This is a small amount of internal memory that is used for the quick storage
and retreival of data and instructions. All processors include
some common registers used for specific
functions, namely the program counter, instruction register, accumulator,
memory address register and stack pointer. For more, click the title above.
This is comprised of the control bus, data bus and address bus. It is used
for connections between the processor, memory
peripherals, and transferal
of data between the various parts. Click the title above for more.
The memory is not an actual part of the CPU itself, and is instead housed
elsewhere on the motherboard. However, it is here that the program
being executed is stored, and as such is a crucial part of the overall
structure involved in program execution. For further information on
the memory, please see the seperate tutorial if available.
For more information on these parts of the
CPU, click the corresponding title of the description above. You could
also click on the part in question on the diagram to the right. Alternatively,
click the right arrow button below to move on to the next page, which
looks at the arithmetic and logic unit.