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What we’ll cover for this lecture topic: What affects overall processing speed? More about physical components. !! KEEP UP with textbook readings !!! The Boot Process.

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computer architecture part 2
What we’ll cover for this lecture topic:

What affects overall processing speed?

More about physical components.

!! KEEP UP with textbook readings !!!

The Boot Process.

If RAM is empty when I turn on the computer, how does the CPU know how to start up and how to load the Operating System? What else happens at boot-up?

Remember RAM’s cousin, ROM?

Excellent text coverage! Read pages 44 - 47.

Computer architecture, part 2
slide2

Register

Register

Adder

Accumulator

Inputs

Outputs

INPUT/PROC/OUTPUT

  • Machine cycle:processing of asingle machine-language instruction
  • In a basic machine:
    • 1 instruction cycle
    • 1 execution cycle

CPU

CU

ALU

0025

operand

35

Pointer

op-code

Address reg

10

35*10=

350

operand

Instr. reg.

op-code operands

Address reg

350

Storage register

Memory

Program 1:

Op-code Operands

Op-code Operands

Op-code Operands …

Data file 1

Aux.

Storage

Program 1

Program 4

Program 2

Data file 1

Program 3

Data file 2

slide3

What affects overall processing speed?

  • The “clock” is one measure of processor speed.
  • CPUs use a digital clock pulse to synchronize the activities of the different hardware units.
  • An ALU performs one step of an execution operation each time a clock pulse occurs.
  • The number of cycles required to process complex instructions varies among instructions (and CPUs).
  • Hence, an complex instruction with 20 steps will have a duration of 20 clock cycles.
  • Number of cycles (Hz) per second: Clock speed
  • EG: 800 MHz clock = 800 million clock ticks/second
    • 800 million steps occur per second (machine cycles)
slide4
Within same processor class, clock speed might be a fair performance indicator:

Within the same processor class, AND if all else is equal, then an 800 MHz processor is almost twice as fast as a 400 MHz processor.

  • So, an 800 MHz processor is twice as fast as a 400 MHz processor, right? Wrong!
    • If an 800 MHz processor requires 15 cycles to perform a complex instruction, it will probably do worse than a 400 MHz processor that requires only 5 cycles for that same complex instruction

5

slide5
Word sizeLonger is better (more manipulated at once)

Number of bits the CPU can store &manipulateas a unit during a single (basic) machine cycle.

Early PCs: “8 bit processor”; then 16 bit (1st IBM PC)

Today’s PCs: 32 bit; latest: 64 bit designs for servers and high-end PCs)

IF all else is equal,a 32-bit processor will be twice as fast as a 16-bit processor.

Bus widthMore is better (more carried at once)

  • Bus: pathways (wires) along which bits (pulses) travel w/in CPU and the rest of computer system.
    • Bus: connects ALU and CU; CPU with memory; input devices with memory; etc.
    • Data bus & Address bus.
      • Note: AddressBUS WIDTH determines amount of addressable memory the CPU can access.
slide7
Main memory More is better!

Today’s apps are memory hogs!

Amount of main memory available to the processor, and its access speed, affects OVERALL performance!

Update of old adage:“You Can never be too rich, too thin, or have TOO MUCH RAM” ;-)

DRAM

dynamic

SRAM

static

  • Cache More is better!
      • Processor idle while it waits for memory access to finish.
      • Cache: logically, lies between CPU and main memory.
      • Computer attempts to keep a copy (in cache) of that portion of main memory that is of current interest.
        • Those transfers normally made between RAM & CPU registers are made between cache and CPU registers instead.
        • “Caching”
        • Expensive---but improves overall processing speed significantly!
slide8

CPU + registers

Cache

Inputs

Primary

Memory

Outputs

Auxiliary Storage

Hard disks, floppy disks, CD-ROMs, tape, ...

Logical organization:(between main memory and CPU)

…lies between

9

slide9

On-chip cache

Off-chip cache

Physical organization:

(can be “on-chip” and/or off-chip)

slide10
Digression: Memory/storage hierarchy

Fastest to slowest access; smallest to largest capacity

Registers

Memory Cache (Level1, Level2)

Primary Memory

Auxiliary (secondary mem.) storage

a hierarchy exists within this category as well : Disk faster than tape; hard disk faster than Floppy disk; etc.)

11

slide11
Other architectural designs that affect speed:

We won’t discuss here….JUST FOR CULTURE

  • Instruction set complexity:CISC and RISC
  • Pipelining
  • Miniaturization
  • Number of processors:
    • Serial: one CPU
    • Parallel: More than one (co-processors or multiple processing units)

12

slide12
Discussing speed

Many functions are measured in terms of how quickly they can be performed during some portion of a second; or, how many can be done in 1 second

  • Millisecond: thousandth
    • ~several milliseconds for disk access
  • Microsecond: millionth
  • memory speed; processor speed for many PCs
  • Nanosecond: billionth
  • processor speed in higher-end PCs
  • Picosecond: trillionth
  • processor speed in supercomputers ***

Quotable!

more about physical components
Transistor: elementary building block.

Solid-state switch—can switch states in less than 20 nanoseconds. Less than 1 micron wide!(0.11-0.25 microns)

Source

“Semi-Conductor”

Gate

Drain

Gate

Drain

Source

CHANNEL

SILICON SUBSTRATE

More about physical components
slide14
The chip: transistors, capacitors, resistors, paths, and other components form the “IC.”

VLSI: level of integration and miniaturization.

Packing it in: less distance for signals to travel = faster.

Electric pulses travel through a wire ~ 1 foot/nanosecond

  • Some chip types (and transistor densities)
    • Memory chips (RAM, ROM, etc…)
        • EG: a 64Mbit IC has 70-80 million transistors
    • Microprocessor chips(CPU for general-purpose PCs)
      • The number of transistors on a chip has increased more than 18,000 times since 1971! For example:
        • 1971: only 2,300 transistors on the 4004 chip
        • 2001: >42million on the Pentium 4; Coming: 214million

15

slide15

Individual transistors—

Newer generation microprocessors (high end:

.18-micron wide transistors,

>42 million transistors/chip.

Pins: connectors that

allow communications with other chips. Plug into circuit board socket.

Package

Circuit board

Bus (commun.

Channels)

The Chip

http://www.intel.com/intel/intelis/museum/

16

slide16
System board

Expansion slot/card or board/port:

NOTE: I will not expect you to memorize all the types of expansion slots, cables, connectors, and ports! Just understand what each is for (a slot, cable, a port….)

Device driver

Graphics card

Printers

Digital Electronics; and Input and Output devices

GOOD textbook coverage:

--Chapter 2 pages 62 thru 64.

--Chap 2 pages 88 thru 96

So we WON’T COVER HERE….

18

slide17
You should understand the jargon better.Example (part of an advertisement in 2005):

Dell Dimension 4700

Processor: Intel Pentium 4 with 2.8 GHz processor

Memory: 256 MB (to 2 GB) SDRAM at 400 MHz

Storage: Ultra Hard drives up to 200 GB

Drive bay options: Dual optical drive bays with your choice of DVD-ROM, CD-RW/DVD or CD-RW/DVD-RW combo

Ports: 6 USB 2.0 ports (2 front & 4 back), one serial port and one parallel port.

Front: digital camera, MP3 player, …

Back: printer, scanner…

Monitors: Up to 21” (19.8” viewable) CRT displays and 19” Flat Panel (19” viewable) displays

Video graphics: …… and Ultra 8X AGP graphics available

Sound: Premium sound cards and brand-name speakers…

Software: pre-loaded with Microsoft Windows XP operating system. Plus you can choose from Corel Works or Microsoft Office XP professional or small bus ed.

Processor Cache: 1 MB (SRAM)

Modem/Network: 56 KB/s or 100Mbit/s

Service and support options….

19