Chapter 1

Introduction

Computer Architecture

• selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals and the formal modelling of those systems.

• Usually concerned with how the central processing unit (CPU) acts and how it accesses computer memory.

• has three main subcategories:i. ISA. Code that a central processor reads and

acts upon. It is the machine language, including the instruction set, word size, memory address modes, processor registers, and address and data formats.

ii. Microarchitecture (Computer Organization) describes the data paths, data processing elements and data storage elements, and describes how they should implement the ISA

iii. System Design incl. all of the other hardware

components within a computing system (datapath, memory controller, data processing (DMA)

ISA

• The interface between the software and hardware.• It is the set of instructions that bridges the gap

between high level languages and the hardware.• For a processor to understand a command, it

should be in binary and not in High Level Language. The ISA encodes these values.

• The ISA also defines the items in the computer that are available to a programmer. For example, it defines data types, registers, addressing modes, memory organization etc.

• Register are high Addressing modes are the ways in which the instructions locate their operands.

• Memory organization defines how instructions interact with the memory.

Computer organization

• helps optimize performance-based products. For example, software engineers need to know the processing ability of processors. They may need to optimize software in order to gain the most performance at the least expense. This can require quite detailed analysis of the computer organization. For example, in a multimedia decoder, the designers might need to arrange for most data to be processed in the fastest data path and the various components are assumed to be in place and task is to investigate the organizational structure to verify the computer parts operates.

Computer organization

• Also helps plan the selection of a processor for a particular project. Multimedia projects may need very rapid data access, while supervisory software may need fast interrupts.

• Sometimes certain tasks need additional components as well. For example, a computer capable of virtualization needs virtual memory hardware so that the memory of different simulated computers can be kept separated.

• The computer organization and features also affect the power consumption and the cost of the processor.

Structure & Function

• Structure is the way in which components relate to each other

• Function is the operation of individual components as part of the structure

• All computer functions are:—Data processing—Data storage—Data movement—Control

Functional View

Operations (a) Data movement

Operations (b) Storage

Operation (c) Processing from/to storage

Operation (d)Processing from storage to I/O

Structure - Top Level

Computer

Main Memory

InputOutput

SystemsInterconnection

Peripherals

Communicationlines

CentralProcessing Unit

Computer

• A machine that had been designed by the people to carry out some numerical and mathematical operations.• The main important part of the computer is the CPU without which nothing can be done.• The other item that comprises the computer are its HW and SW.

CPU

Structure - The CPU

Computer Arithmeticand Login Unit

ControlUnit

Internal CPUInterconnection

Registers

CPU

I/O

Memory

SystemBus

CPU

• portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. • plays a role somewhat analogous to the brain in the computer.• Two typical components: i- ALU (performs arithmetic and logical operations) ii- CU (extracts instructions from memory and decodes and executes them, calling on the ALU when necessary.

Structure - The Control Unit

CPU

ControlMemory

Control Unit Registers and Decoders

SequencingLoginControl

Unit

ALU

Registers

InternalBus

Control Unit

• The control unit of the CPU contains circuitry that uses electrical signals to direct the entire computer system to carry out stored program instructions. • It does not execute program instructions; rather, it directs other parts of the system to do so. • Must communicate with both the arithmetic/logic unit and memory.

Processor Register o A small amount of storage available as part of a CPU. - Such registers are typically addressed by other mechanisms than main memory and can be accessed more quickly. - Almost all computers, load-store architecture or not, load data from a larger memory into registers where it is used for arithmetic, manipulated, or tested, by some machine instruction. - normally at the top of the memory hierarchy, and provide the fastest. This refers only to the group of registers that are directly encoded as part of an instruction, as defined by the instruction set. way to access data.  - normally measured by the number of bits they can hold. eg: an "8-bit register" or a "32-bit register".