CPU Architecture - Basic

1. CPU Architecture -
Basic
Yong Heui Cho @ Mokwon University
Some of slides are referred to:
[1] The CPU, slideshare.

2. Basic Computer Design
4. Combinational Logic Circuit
5. Sequential Logic Circuit
6. CPU Architecture - Basic
7. CPU Architecture -
Advanced

3. CPU?
3
□ Courtesy to The CPU, slideshare.
• The CPU is short for the Central Processing Unit.
• It is the main part of the computer where instructions ar
e processed.
• The central processing unit includes the main memory.
• Now a day’s most computers have more than one CPU to
provide better speed.

4. Microprocessor
4
• Small computerised devices such as washing mac
hines have small specialised CPUs known as micr
oprocessors.
• It is an integrated circuit as a single unit which i
ncludes all that the CPU needs excluding main m
emory.
□ Courtesy to The CPU, slideshare.

5. Components of CPU
5
• The CPU is made up of many components such
as
1. Arithmetic logic unit (ALU)
2. Control unit (CU)
3. Registers (Program Counter and Instruction Register)
4. Cashes
5. Buses
□ Courtesy to The CPU, slideshare.

6. 6□ Courtesy to The CPU, slideshare.

7. Control Unit (CU)
7
• The CU is considered the manager of the CPU
• The CU’s jobs
1. decode instructions within a computer
2. plan the reading and writing of data
3. control the order in which instructions are executed
4. control the operations performed by the ALU
• In the CU you will fine two registers;
1. Instruction Register: stores a copy of the current instruction being
performed
2. Program Counter
□ Courtesy to The CPU, slideshare.

8. Arithmetic Logic Unit
8
• The ALU is that part in the CPU where arithmetic and logic op
erations are carried out in other words all mathematical calcul
ations. The result of the calculations are sent to the main mem
ory.
• The ALU is capable of performing:
1. Addition, Subtraction, Multiplication, Division
2. Greater Than (>), Smaller Than (<)’ Equal (=),Greater Than or Equ
al To (>=), Smaller Than or Equal To (<=), Not Equal (<>)
3. AND, OR, NOT
• Within the ALU we will find the register known as the Accum
ulator. The accumulator stores the result of the current calcula
tion.
□ Courtesy to The CPU, slideshare.

9. Program Counter
9
• The program counter is sometimes known as the instruction p
ointer.
• The PC indicates where the computer is in its instruction set. If
the instruction set has 5 steps the PC will point to which step t
he computer has arrived.
• Depending on the device the PC could hold
1. the address of the instruction being executed
2. the address of the next instruction to be executed
• The program counter is automatically incremented (increased
by 1) after each step (instruction cycle).
□ Courtesy to The CPU, slideshare.

10. Instruction Register
10
• The instruction register (IR) is also found with t
he control unit
• The IR is used to store a copy of the current inst
ruction being performed
• This instruction is stored in the for of operator
and operand (covered later on)
□ Courtesy to The CPU, slideshare.

11. Buses
11
• All data traffic with the CPU takes place across the computer’s
bus
• A computer bus is a set of parallel electrical tracks connecting
components within a computer
• The width of the data bus determines the word length
• The width of the address bus determines how many addresses t
he computer can send at a time
□ Courtesy to The CPU, slideshare.

12. Simplified Architecture
12□ Courtesy to The CPU, slideshare.
IR
data
Control Unit (CU)
ALU