Computer Abstractions and Technology

personal computer

general purpose, variety of software, subject to cost/performance tradeoff

server computer

network based, high capacity, performace, reliability, rangle from small to building size

supercomputer

type of server, high-end calculations, highest capability

embedded computer

hidden as components of systems, power/performace/cost restraints

Personal Mobile Device (PMD)

battery operated, connects to internet, $100s

cloud computing

warehouse scale computers, software as a service, portion runs on PMD, portion on Cloud

Algorithm

determines number of operations executedprogr

programming language, compiler, architecture

determine number of machine instructions executed per operation

processor and memory system

determine how fast instructions are executes

I/O system

determines how fast I/O operations are executed

Seven Great Ideas

abstraction, common case fast, parallelism, pipelining, prediction, heirarchy, dependability

abstraction

breaking down complex systems into smaller, manageable components

common case fast

optimization of frequent operations

parallelism

performing multiple tasks simultaneously to increase speed

pipelining

overlapping execution of instructions to reduce time it takes to complete thempredi

prediction

making educated guesses about future events to avoid waiting

heirarchy of memories

organizing memory into different levels based on speed and cost

dependability

using multiple components to increase reliability

application software

written in high level language

system software

compiler and operating system

compiler

translates HLL code to machine code

operating system

service code - handles input/output, manages memory and storage, schedules tasks & sharing resources

hardware

processor, memory, I/O controllers

High-level language code

level of abstraction closer to problem domain, provides productivity and portability

assembly language code

textual representation of instructions

hardware representation of code

binary digits (bits), encoded instructions and data

components of a computer

desktop, server, embedded

Input/Output includes

user-interface devices, storage devices, network adapters

user interface devices

display, keyboard, mouse

storage devices

hard disk, CD/DVD, flash

network adapters

for communicating with other computers

Touchscreen

PostPC device, supersedes keyboard/mouse, resistive and capacitative types

LCD screen

picture elements (pixels), mirrors content of frame buffer memory

Inside the Processor (CPU)

Datapath, Control, Cache memory

datapath

performs operations on data

control

sequences datapath, memory

cache memory

small fast SRAM memory for immediate access to data

instruction set architecture (ISA)

hardware/software interface

application binary interface

the ISA plus system software interface

implementation

the details underlying and interface

volatile main memory

loses instructions and data when powered off

non-volatile secondary memory

magnetic disk, flash memory, optical disk (CDROM, DVD)

networks

communication, resource sharing, nonlocalaccess

local area network (LAN)

ethernet

wide area network (WAN)

internet

wireless network

wifi, bluetooth

electronics technology evolves

increased capacity and performance, reduced cost

can transform silicon to act as

codnuctor, insulator, switch

yield

proportion of working dies per wafer

die

single Integrated Circuit (IC)in

integrated circuit cost

nonlinear relation to area and defect rate

fewer dies per wafer

as die area increases, you get fewer chips from a singular wafer

lower yield

as the die area increases, the defect rate increases as the likelihood of there beign a defect on the die increases

response time

how long it takes to do a task

throughput

total work done per unit time

elapsed time

total response time, determines system performance

aspects of response time

processing, I/O, OD overhead, idle time

CPU Time

time spent processing a given job, comprises user and system CPU time

CPU clocking

operation of digital hardware governed by constant rate clock

cycle time

duration of a clock cycle

clock rate

clock frequency

CPU performance improved by

reducing number of clock cycles, increasing clock rate (clock cycles/clock rate)

instruction count

determined by program, ISA, and compiler

average cycles per instruction (CPI)

determined by CPU hardware, use average CPI affected by instructions

performance depends on

algorithm, programming language, compiler, instruction set architecture

power

capacitative load x voltage² x frequency

the power wall

cannot reduce voltage further, cannot remove more heat

uniprocessor performance

constrained by power, instruction-level parallelism, memory latency

multicore microprocessor

has more than oen processor per chip, requires parallel programming

thread-based parallelism

divide tasks into multiple threads that can run on separate cores

data parallelism

workloads are split across cores to process data in chunks - GPU computing

task parallelism

tasks are assigned to different cores - thread for UI, thread for computations

Spectre vulnerability

exploits speculative execution capabilities of modern CPUs, leak sensitive data

instruction level parallelism (ILP)

executing multiple instructions within a single processor core using pipelining, superscalar execution, out-of-order execution

SPEC Power Benchmark

industry-standard tool designed to evaluate the energy efficiency of server-class computers

SPECpower_ssj2008

most recognized version of SPEC Power Benchmark

Amdahl’s Law

improving an aspect of a computer and expecting a proportional improvement in overall performance

MIPS pitfall - Millions of Instructions Per Second

doesn’t account for differences in ISAs between computers, differnces in complexity between instructions

process

an independent program in execution with its own memory space

thread

a lightweight unit of execution within a process, sharing the process’ resources

multi-process architecture

create separate processes for different tasks