Computer Architecture - Computational Sciences - Lecture Slides, Slides of Computational Techniques

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Computer Architecture

What

is

a

digital

computer

A

digital

computer

is

a

machine

composed

of

the

following

three

basic

components

Input/Output

Central

Processing

Unit

(CPU)

Memory

the concepts of mechanical control and mechanical calculation put together into a machine that has the basic parts of a digital computer - He was given 17, Pounds to construct the machine but, the project was abandoned in 1842 (uncompleted) - 1856, Babbage conceived the idea of the Analytical Machine (After his death his son Henry tried to build it but never succeeded) - In 1854, George Scheutz, built a working Difference machine based on Babbage’s design. ( This machine printed mathematical, astronomical and actuarial tables with unprecedented accuracy,and was used by the British and American governments)

Between 1847 and1849 Babbagedesigned theDifference EngineNo.2.He did not built it Difference Engine No.

The

John

von

Neumann

Architecture

consists

of

five

major

components

(1940s)

A

refinement

of

the

von

Neumann

model,

the

system

bus

model

has

a

CPU

(ALU

and

control),

memory,

and

an

input/output

unit

The

CPU

CPU

(central processing unit) is an older term for processor and microprocessor, the central unit in a computer containing the logic circuitry that performs the instructions of a computer's programs.

NOTABLE

TYPES

RISC:

Reduced Instruction Set Computer ‐ Introduced in the mid 1980s ‐ Requires few transistors ‐ capable of executing only a very limited set of instructions ‐

CISC:

Complex Instruction Set Computer ‐ complex CPUs that had ever

larger sets of instructions

RISC or CISC “The great Controversy”

RISC

proponents argue that

RISC

machines are both cheaper and faster, and are therefore the machines of the future.

Skeptics note that by making the hardware simpler,

RISC

architectures put a greater burden on the software. They argue that this is not worth the trouble because conventional microprocessors are becoming increasingly fast and cheap anyway.

The

TRUTH!

CISC

and

RISC

implementations are becoming more and more alike. Many of today's

RISC

chips support as many instructions as yesterday's

CISC

chips. And today's

CISC

chips use many techniques formerly associated with

RISC

chips.

What you need to Know about a CPU

Processing speed ‐ The clock Frequency is one measure of how fast a computer is ( however, the length of time to carry out an operation depends not only on how fast the processor cycles, but how many cycles are required to perform a given operation. - Voltage requirement Transistors (electronic switches) in the CPU requires some voltage to trigger them. ‐ In the pre ‐ 486DX days, everything was 5 volts ‐ As chips got faster and power became a concern, designers dropped the chip voltage down to 3. volts (external Voltage) and 2.9V or 2.5V core voltage docsity.com

More on Voltage Requirements…

Power consumption equates largely with heat generation, which is a primary enemy in achieving increased performance. Newer processors are larger and faster, and keeping them cool can be a major concern. - Reducing power usage is a primary objective for the designers of notebook computers, since they run on batteries with a limited life. (They also are more sensitive to heat problems since their components are crammed into such a small space). - Compensate for by using lower ‐ power semiconductor processes, and shrinking the circuit size and die size. Newer processors reduce voltage levels even more by using what is called a dual voltage , or split rail design docsity.com

Power consumption verses speed of some processors

MEMORY

Computers have hierarchies of memories that may be classified according to Function, Capacity and Response Times. ‐ Function "Reads" transfer information from the memory; "Writes" transfer information to the memory: ‐ Random Access Memory

(RAM)

performs both reads and writes. ‐ Read

Only Memory

(ROM)

contains information stored at the time of manufacture that can only be read. ‐ Programmable Read

Only Memory

(PROM)

is

ROM

that can be written once at some point after manufacture. ‐ Capacity bit

smallest unit of memory (value of

or

byte

bits; In modern computers, the total memory may range from say

MB

in a small personal computer to several

GB

(gigabytes) in large supercomputers.

The

I/O

BUS

A Computer transfers data from disk to CPU, from CPU to memory, or from memory to the display adapter etc. To avoid having a separate circuits between every pair of devices, the BUS is used. Definition: The Bus is simply a common set of wires that connect all the computer devices and chips together