Transcript CA_mod02_CSC1

Computer Architecture
Lecture Notes
Spring 2005
Dr. Michael P. Frank
Competency Area 1:
Computer System Components
Why Study Computer Architecture?
• According to William Stallings text, the
IEEE/ACM Computer Curricula 2001 Joint Task
Force reported the following:
The computer lies at the heart of computing. Without it most of the computing
disciplines today would be a branch of theoretical mathematics. To be a
professional in any field of computing today, one should not regard the
computer as a just a black box that executes programs by magic. All students
of computing should acquire some understanding and appreciation of a
computer system’s functional components, their characteristics, their
performance, and their interactions. Students need to understand computer
architecture in order to structure a program so that it runs more efficiently on a
real machine. In selecting a system to use, they should be able to understand
the tradeoffs among various components, such as CPU clock speed versus
memory size.
Computer System Components
• In most generalizations of computers, there are
essentially five classic components that are designed:
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Input Systems (e.g. keyboard, mouse)
Output Systems (e.g. Monitor display, printer)
Memory (contains stored programs and memory)
Control (component that controls memory, I/O, datapath)
Datapath (component that performs arithmetic operations)
Computer System Components
• Some Terminology & General Definitions:
Because of the binary nature of computers, we typically use
powers of 2 to represent large and small numbers. However,
normal usage requires powers of 10 expressions. For example, we
often use powers of 2 for describing memory
capacities and powers of
10 for clock frequencies.
Computer System Components
• A byte refers to 8 bits. A nibble is half a byte or 4 bits.
• A word is a group of bits that is processed
simultaneously. Typical words sizes are 8, 16, and 32.
• Bits in a word can be numbered from left to right (little
endian) or from right to left (big endian).
• The leftmost bit is called the Most Significant Bit (MSB).
• The rightmost bit is called the Least Significant Bit
(LSB).
• Other terms – UNITS: seconds (s), bits (b), bytes (B),
words (w). For example, Gb/s; ns; MB; Mb
• Reciprocal seconds are called Hertz (Hz), so a clock
period of 100ns corresponds to a clock rate of 10 MHz.
Computer System Components
• Bits are used to represent both instructions and data.
• Initially only binary numbers are used to design and
program computers, however this became tedious.
Hence, the development of assembly language and
high-level programming languages.
• The notion of low-level and high-level programming is a
common approach to hardware and software system
design.
• A system that consists of hierarchical layers with each
lower layer hiding the details from the layer above it is
known as abstraction.
Computer System Components
• Levels or layers of Abstraction can be though of as the
highest “user” level to the lowest level (transistor level).
• Separability is the key to effective computer abstraction.
For example, if you run Microsoft Word or some other
word processing program, you don’t need to know
anything about the inner-workings of its programming.
• Exploiting separability supports the development of
upwardly-compatible machines (allows a user to upgrade
to a faster, more capable machine without rewriting the
software the runs on the less capable machine)
Computer System Components
Highest Level
User Level – Applications Programs
High-level Languages
Assembly Language/Machine Code
Mircoprogrammed/Hardwired Control
Functional Units (memory, ALU, etc.)
Logic Gates
Lowest Level
Transistors and Wires
Computer System Components
• To understand and appreciate computer systems, we
must study the computer from several different aspects:
— USER Perspective
+ User Level and Applications; High-level Languages
— Machine Language Programmer’s
Perspective
+ Assembly Language/Machine Coding
— Computer Architect’s Perspective
+ Hardwired Control and Functional Units; Performance
— Computer Logic Designer’s Perspective
+ Logic Gates, Transistors and Wires
Computer System Components
• Let’s continue our discussion of the computer from a
USER’S PERSEPECTIVE:
The user is the person who is using the computer to perform
useful work.
- The user is not concerned about the internal structure of the
machine. Only that it is capable of performing applications such
word processing, spreadsheets, programming, etc.
- The user is interested in the operating system and the application
software.
- This perspective is only aware of:
- Computer Speed (how fast will the computer run my programs)
- Storage Capacity (how much data can I store in computer)
- Behavior of peripheral devices (can I send data to a printer, etc.)
Computer System Components
• Consider the MACHINE LANGUAGE PROGRAMMER’S
PERSEPECTIVE:
The machine language programmer is concerned with the
behavior and performance of the computer system when it is
programmed at the lowest level (machine language).
- To fully understand this perspective, we must define
some terms:
- Machine Language: The collection of all the fundamental
instructions that the machine can execute, expressed as a pattern
of 1’s and 0’s.
- Assembly Language: The alphanumeric equivalent of the machine
language. Alphanumeric mnemonics are used as an aid to the
programmer, instead of 1’s and 0’s.
- Assembler: A computer program that converts assembly language
to machine language.
Computer System Components
• Let’s examine some assembly language instructions:
MIPS Assembly
Language
Machine Language
ADD
$t0, $s2, $s3
000000 10010 10011 01000 00000 100000
LW
$s1, 100($s2)
100011 10010 10001 00000 00001 100100
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The first instruction adds the contents of 32-bit register $s2 to the contents
of register $s3 and places the sum in register $t0. A register is a storage
unit capable of holding a collection of bits. Registers $s2, $s3, and $t0 are
known as operands.
•
The corresponding machine language is shown. The first field is known as
the operational code (a.k.a opcode). The opcode specifies the particular
operation to be performed.
•
We will learn more about assembly language programming and coding later
when we discuss instruction set architectures.
•
Assembly languages and machine codes are specific to the architecture
that is being used.
Computer System Components
• The collection of all the operations in a machine’s
language is its instruction set.
• A programmer is concerned with the machine and
assembly language instruction set, as well as the
machine resources that can be managed with those
instructions.
• The collection of instructions and resources is known as
the Instruction Set Architecture (ISA) of a computer,
which includes:
– Instruction Set
– Machine’s memory
– All programmer-accessible registers in the CPU
Computer System Components
•
The “tools of the trade” for the machine language
programmer’s perspective are the following:
1. ASSEMBLER – translates assembly language statements to
their binary equivalent.
2. LINKER – links separately assembled modules into a single
module suitable for loading and execution. Essentially,
translating high-level languages (e.g. C++, FORTRAN) into
programs capable of execution.
3. DEBUGGER – Low-level programs that perform error-checking
of assembly language programs allowing programmer to
perform step-by-step troubleshooting techniques.
4. DEVELOPMENT SYSTEMS – collection of hardware and
software tools that is used to support system development.
Computer System Components
• Consider the COMPUTER ARCHITECT’S PERSEPECTIVE:
The computer architect is concerned with the design and
performance of the computer system as a whole.
- The architect’s job is to design a system that will provide
optimum performance in the context of its users. This is
essentially known as the “constrained optimization
problem”.
- The constraints may include:
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Cost
System Size
Memory Capacity
Thermal or mechanical durability
Availability of components
Immunity static charge
Time to completion
Computer System Components
• From given constraints, performance specifications are defined such
as processing speed, memory size, networkability, graphics
resolution, etc.
• Architects use performance measurement tools to determine
whether systems meet to specs identified. Usually these include
benchmarks, simulations, etc. These are the “tools of the trade” for
architect’s.
• Key Concepts:
– The architect is responsible for the overall system design and
performance.
– Performance must be measured against quantifiable specifications.
– The architect is likely to become involved in low-level details of of
the computer design.
– The architect often uses formal description languages (e.g. RTL) to
convey details of the design to other parts of the design team.
– The architect strives for harmony and balance in system design.
Computer System Components
• Consider the COMPUTER LOGIC DESIGNER’S
PERSEPECTIVE:
The computer logic designer is concerned about the machine
at the logic gate level. Usually the computer architect takes
the role of the logic designer because their functions overlap.
- The logic designer deals with the implementation
domain, which is a collection of hardware devices that
make up a machine.
- The logic gate implementation domain may be
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VLSI on silicon
Transistor-transistor logic (TTL) chips
Emitter-coupled logic (ECL)
Programmable logic arrays (PLAs)
Optical switches, etc.
Computer System Components
• The implementation domain is important because of the
translation of the abstract level of logic gates to the
concrete or practical domain.
• How can we most efficiently implement the logic gate
design needed for the system using the hardware
available?
• For example, if a designer is implementing a system
using VLSI on silicon, the number and size of the
processor’s registers may be affected by the amount of
silicon is available on the chip.
• Tools of the trade for the designer include CAD tools and
IC design tools.
Computer System Components
• Our primary concern in this class includes
– Assembly language programming
– System design and performance
• We’ll discuss some aspects of the logic designer’s
perspective such as gate–level implementation of
arithmetic operations.
• Other aspects of logic designer’s view is covered in
courses like FPLDs, IC Design (Mixed and Digital), DSP
for FPGAs, etc.
• The user’s perspective is covered in courses like C
programming and MATLAB design.
• Next time we’ll look different computer architectures
from an historical perspective…
Class Exercise
Answer the following questions based on the
information presented in today’s lecture:
1. How many bytes are contained in a 32-bit word?
2. The Tolstoy novel War and Peace has 696 pages. A
CD-ROM can store approximately 600 MB of
information. One character can be stored in one byte.
Can the contents of the book be stored on a single CDROM? Show your calculations. (Assume each page
contains 50 lines and there are approximately 100
characters per line.)