COMP ORG UNIT IV( 2ND SEM MIDTERM)

Unit IV – Computer Architecture

A. Computer Structure and Architecture

A. Computer Structure and Architecture

The basic function of a computer is to run a program code in the specified sequence. In other words, it reads, processes, and stores the needed data.

Basic computer structure

Basic Computer structure

Basic computer structure:

• Main memory - Closely located to the CPU, it consists of memory semiconductor chips.

• Auxiliary storage device - The secondary storage device can be accessed at a low speed because it includes mechanical devices.

• I/O device - consists of an input device and an output device to be used as the tool for interaction between the users and computers.

• Closely located to the CPU, it consists of memory semiconductor chips.

Main memory

• The secondary storage device can be accessed at a low speed because it includes mechanical devices

Auxiliary storage device

• consists of an input device and an output device to be used as the tool for interaction between the users and computers.

I/O device

2 Types of computer architecture:

• Von Neumann Architecture

• Harvard Architecture

The CPU can read commands from the memory and can read and write data both from the memory and to the memory Instructions and data cannot be accessed simultaneously because they use the same signal bus and memory.

Von Neumann architecture

It solves computer bottlenecks by storing commands and data in different memories and improves performance by reading and writing commands in parallel, However, the bus system design becomes complex.

Harvard architecture

Computer Structure Applying Both Harvard and Von Neumann Architecture

they separate the cache memory for instruction and data, and they apply the Harvard architecture inside the CPU (CPU and cache) and the von Neumann architecture outside CPU (CPU and memory).

B. CPU

The __ is the most important part of computers, as it interprets instructions and handles arithmetic or logical operations and data processing. It plays the key role of running programs and processing data.

CPU

CPU operation is divided into a function that commonly runs for al instructions, and a function that runs only when necessary, according to the instructions.

ENUMERATE THE CPU COMPONENTS

• control unit

• arithmetic logic unit (ALU)

• registers

• buses

A hardware module that sequentially generates control signals to interpret the program codes (instructions) and run them.

Control unit

A key element of the CPU to execute arithmetic operations and logical operations

Arithmetic Logic Unit

A temporary storage area that temporarily stores instructions waiting to be processed by the CPU or the Intermediate result values of the CPU operation.

Register

The register types include:

• PC (program counter)

• (instruction register),

• AC (accumulator)

• MAR (memory address register)

• MBR (memory buffer register)

• SP (stack pointer).

A common transmission line that connects the CPU, memory, /O unit, etc, in order to exchange necessary data.

Bus

CPU STRUCTURE MODEL

This is the entire process required for the CPU to execute an instruction.

Instruction cycle

<Table 10> shows the entire instruction cycle. The CPU components needed in each cycle are different.

refers to the machine language instructions that a microprocessor can recognize, understand its function, and execute.

Instruction set, or instruction set architecture (ISA),

embeds many complex instructions into the hardware in order to process the complex instructions as a single instruction.

complex instruction-type computer ( CISC)

embeds a few simple instructions into the hardware to process complex instructions as a set of simple instructions.

reduced instruction-type computer ( RISC)

C. Memory

the memory unit at a higher level has a higher price per bit, less capacity, a shorter access time, and a higher access frequency by the CPU.

Memory unit’s hierarchical structure

Factors for performance evaluation of memory unit

• Capacity

• Access time

• Cycle time

• The bandwidth of the storage unit

• Data transportation

• Cost

Memory units can be classified according to the use, physical storing method, data retention, and content preservation.

Type and characteristics of the memory unit

the location in the main memory where data is stored. Various addressing methods are available to designate instructions, using limited instruction bits and using the memory unit capacity efficiently.

Address

The ___ is a tendency in which programs intensively refer to a specific area in the moment, rather than uniformly accessing information in the memory device.

locality

Recently accessed programs or data are more likely to be accessed again in the near future.

Temporal locality:

Data stored adjacent to the storage device is more likely to be accessed continuously.

Spatial locality:

Instructions are fetched and executed in the order in which they were stored, unless branched (about 20%).

Sequential locality:

D. I/O Device

The device is necessary to perform an input operation that stores data to be processed by the CPU in the memory unit, as well as an output operation that transfers the processing results from the main memory to an output medium.

An I/O controller is necessary to process inputs and outputs, as shown in [Figure 36], and it plays the following roles:

• I/O device control and timing coordination

• Communication with the CPU

• Communication with the I/O device

• Data buffering

• Error detection

I/O controller structure and addressing method

• Memory-mapped I/O

• I/O mapped I/O:

It is a method of allocating a part of the address area in the memory to the register addresses in the I/O controller. It has the advantage of easy programming, but the disadvantage of reducing the available memory space.

Memory mapped I/O:

It is a method of allocating the I/O device address space separately from the memory address space. It has the advantage of not reducing the available memory address space, but the disadvantage of making it difficult to program.

I/O MAPPED I/O

a method of the I/O device directly accessing the memory without the assistance of the CPU.

DMA- Concept of DMA

DMA OPERATION SEQUENCE

DMA OPERATION MODE

E. Latest Technologies and Trends

a new semiconductor type that processes information in a way that is similar to human thinking, by implementing brain behavior in silicon as much as possible.

Neuromorphic chip

new conceptual computer that can simultaneously process a large volume of information at a high speed, based on the principle of ultra-high-speed, large-capacity computing technology optimized for specific operations, according to the principle of overlapping and entanglement inherent in quantum mechanics.

Quantum computer