1.3 Types of Processors

Question 1

Who and when was the stored program concept introduced?

Answer 1

1940s, John von Neumann and Alan Turing

Question 2

Stored program concept

Answer 2

• A program must be loaded into main memory to be executed by the processor
• Instructions are fetched one at a time, decoded and executed sequentially by the processor
• The sequence of instructions can only be changed by a conditional or unconditional jump instruction

Question 3

What is the most common implementation of the stored program concept?

Answer 3

von Neumann architecture

Question 4

von Neumann architecture

Answer 4

Instructions and data are stored in a common main memory and transferred using a single shared bus

Question 5

Harvard architecture

Answer 5

Program instructions are no longer competing for the same bus

Question 6

Where are the Harvard architecture principles implemented?

Answer 6

In embedded systems and digital signal processing (DSP), where speed is more important in the design

Question 7

Advantages of von Neumann architecture

Answer 7

• Owing primarily to cost and programming complexity, almost all general purpose computers are based on von Neumann’s principles
• Simplifies the design of the Control Unit
• Data from memory and from devices are accessed in the same way

Question 8

What do most modern CPU architectures utilise (stored program concept)?

Answer 8

• Both aspects of von Neumann and Harvard architecture
• Cache is split into instruction and data cache
• Main memory holds both data and instructions (some digital processors have multiple parallel data buses (2 write, 3 read) and one instruction bus

Question 9

CISC (Complex Instruction Set Computers)

Answer 9

• A large instruction set is used to accomplish tasks in as few lines of assembly language as possible
• A CISC combines a “load/store” instruction with the instruction that carries out the actual calculation

Question 10

RISC (Reduced Instruction Set Computers)

Answer 10

A minimum number of very simple instructions, each taking one clock cycle, are used to accomplish all the required operations in multiple general purpose registers.

Question 11

Advantages of RISC

Answer 11

• Quicker to code programs
• Compiler has very little work to do to translate a high-level language statement into machine code
• Because the code is relatively short, very little RAM is required to store the instructions

Question 12

Advantages of RISC

Answer 12

• The hardware is simpler to build with fewer circuits needed for carrying out complex instructions
• Because each instruction takes the same amount of time, pipelining is possible
• Ram is now cheap, and RISC use of RAM and software allows better performance processors at less cost

Question 13

Parallel systems

Answer 13

Multi-core processors are able to distribute workload across multiple processor cores, thus achieving significantly higher performance by performing several tasks in parallel

Question 14

How does a computer use parallel processing?

Answer 14

Software has to be written to take advantage of multiple cores (for example using tabbed browsing can make cores simultaneously process requests, videos or running software in different windows)

Question 15

Co-processor systems

Answer 15

An extra processor used to supplement the functions of the primary proessor

Question 16

GPU (Graphics Processing Unit

Answer 16

• A specialised electronic circuit which is very efficient at manipulating computer graphics and image processing
• Consists of thousands of small efficient cores designed for parallel processing
• Can process large blocks of visual data simultaneously

Question 17

Function of GPU

Answer 17

• They are used in numerous devices ranging from phones and tablets to cars, drones and robots
• A GPU can act together with a CPU to accelerate scientific, engineering and other applciations