CPU, CONTROL UNIT, ALU

BY: GROUP 10 (MT - 2A)Grado, Crystell Joy

Jimenez, Faye AlyannaUy, Christina Marie

Central Processing Unit (CPU)

• The central processor, but more commonly called  processor.

Brain of the computer

Central Processing Unit (CPU)

• It is the most important element of a computer system.

• On large machines, the CPU requires one or more printed circuit boards.

• On personal computers and small workstations, the CPU is housed in a single chip called a microprocessor.

The world's first CPU was introduced by Intel in 1971. The Intel 4004 was a 4-bit CPU, clocked at 740 KHz and capable of executing up to 92,600

instructions per second. Five months after the Intel 4004, the Intel 8008

was introduced. This was the world's first 8-bit microprocessor.

Marcian Edward "Ted" Hoff, Jr.• One of the inventors of

the microprocessor.• Came up with the idea of using a

"universal processor" rather than a variety of custom-designed circuits.

• His insight started the microprocessor revolution in the early 1970s.

Basic CPU Components

• Arithmetic Logic Unit (ALU)• Control Unit (CU)• Register - A special, high-

speed storage area within the CPU. All data must be represented in a register before it can be processed.

• Interface – which communicate with external memory, I/O units, and possibly other CPU’s.

CPU Clock Speed• Also called clock rate• the speed at which a microprocessor

executes instructions. • Every computer contains an internal clock that

regulates the rate at which instructions are executed and synchronizes all the various computer components.

• The CPU requires a fixed number of clock ticks (or clock cycles) to execute each instruction.

• The faster the clock, the more instructions the CPU can execute per second.

• Clock speeds are expressed in megahertz (MHz) or gigahertz (GHz).

• Processors were originally developed with only one core. Multi-core processors were developed in the early 2000s by Intel, AMD and others. Multicore processors may have two cores (dual-core CPUs, for example AMD Phenom II X2 and Intel Core Duo), four cores (quad-core CPUs, for example AMD Phenom II X4, Intel's i5 and i7 processors), six cores (hexa-core CPUs, for example AMD Phenom II X6 and Intel Core i7 Extreme Edition 980X), eight cores (octo-core CPUs, for example Intel Xeon E7-2820 and AMD FX-8350), ten cores (for example, Intel Xeon E7-2850), or more. A multi-core processor implements multiprocessing in a single physical package. 

How CPU Works…• The CPU is centrally located on the

motherboard. Since the CPU carries out a large share of the work in the computer, data continually pass through it. The data comes from the RAM and the units (keyboards, drives, etc.). After processing, the data is sent back to the RAM and the units.

• The CPU continually receives instructions to be executed. Each instruction is a data processing order. The work itself consists mostly of calculations and data transport.

The Instruction-Execution Cycle• Many types of personal computers can execute

instructions in less than one-millionth of a second; supercomputers can execute instructions in less than one-billionth of a second.

• The CPU performs four steps in executing an instruction:

1. The CU gets the instruction from the memory.2. The CU decides what the instruction means and

directs the necessary data to be moved from the memory to the ALU.

3. The ALU performs the actual operation on the data.4. The result of the operation is stored in memory or

a register.

• The first two instructions make up what is called the instruction time. The last two instructions make up what is called the execution time. The combination of these two is called a machine cycle.

• Each CPU has an internal clock (or system clock), which produces pulses at a fixed rate to synchronize all computer operations. A single machine cycle instruction is made up of sub instructions, each of which must take at least one clock cycle.

• Each type of CPU is designed to understand a specific group instruction called the instruction set.

How the CPU finds Instructions and Data

• The location in the memory for each instruction and each piece of data is identified by an address, or a number that stands for a location in the computer memory.

• An address may be compared to a mailbox in everyday life, except that the address can hold only one item – a fixed amount of data, a number or a word – at any one time.

Control Unit (CU)

The control unit is a component of a computer's central processing unit (CPU) that directs operation of the processor. It controls communication and co-ordination between input/output devices. It reads and interprets instructions and determines the sequence for processing the data.

Control Unit (CU) cont’d

It is a typical component of the CPU that implements the microprocessor instruction set. It extracts instructions from memory and decodes and executes them and sends the necessary signals to the ALU to perform the operation needed. Control units are either hardwired (instruction register is hardwired to rest of the microprocessor) or micro-programmed.

Arithmetic Logic Unit(ALU)• ALU Concept was proposed by John Von

Neumann in 1945 when he was writing a report on the foundations of EDVAC.

• Fundamental building block of the Central Processing Unit (CPU).

• The simplest microprocessors contain one ALU for purposes such as maintaining timers.

• Modern computers contain very powerful and complex ALUs and a control unit.

Arithmetic Logic Unit (ALU)

Functions of the Arithmetic Logic Unit

• The part of a computer that performs all arithmetic and logic computations (addition, multiplication, comparison operations like not, and, and or).

• Performs most of the operations of a CPU.