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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
Peripherals
Computer
Central
Processing
Unit
Computer
Communication
lines
Main
Memory
Systems
Interconnection
Input
Output
• 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
CPU
Computer
I/O
System CPU
Bus
Memory
Arithmetic
and
Login Unit
Internal CPU
Interconnection
Registers
Control
Unit
• 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
Control Unit
CPU
ALU
InternalControl
Bus Unit
Registers
Sequencing
Login
Control Unit
Registers and
Decoders
Control
Memory
• 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".