Transcript More about Processing

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.
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INPUT/PROC/OUTPUT
single machine-language instruction
CPU
0025
CU
35
Register
Address reg
op-code
Instr. reg.
operand
op-code operands
In a basic machine:
1 instruction cycle
1 execution cycle
ALU
operand
Pointer
Machine cycle: processing of a
Address reg
35*10=
350
Adder
Storage register
10
Register
350
Accumulator
Memory
Program 1:
Inputs
Op-code Operands
Op-code Operands
Op-code Operands …
Data file 1
Program 1
Program 2
Program 3
Outputs
Program 4
Aux.
file 1
Storage Data
Data file 2
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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)
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– 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
– 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.
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Word size
Longer is better (more manipulated at once)
• Number of bits the CPU can store & manipulate as 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 width
More 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: Address BUS WIDTH determines amount of
addressable memory the CPU can access.
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Main memory DRAM
dynamic
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” ;-)
Cache
SRAM
static
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!
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Logical organization:
(between main memory and CPU)
CPU + registers
Cache
Inputs
…lies between
Primary
Memory
Outputs
Auxiliary Storage
Hard disks, floppy disks, CD-ROMs, tape, ...
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Physical organization:
(can be “on-chip” and/or off-chip)
On-chip cache
Off-chip cache
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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.)
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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)
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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!
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More about physical components
• Transistor: elementary building block.
Drain
“Semi-Conductor”
Gate
Source
– Solid-state switch—can switch states in less than 20
nanoseconds. Less than 1 micron wide!
(0.11-0.25 microns)
Gate
Drain
CHANNEL
Source
SILICON SUBSTRATE
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• 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: >42 million on the Pentium 4; Coming: 214 million
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Individual transistors—
The Chip
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)
http://www.intel.com/intel/intelis/museum/
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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….
• 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
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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….
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