Memory and PeripheralsMemory and Peripherals

COSC-100 (Elements of Computer Science)

Prof. Juola

Basic OrganizationBasic Organization

• We’ve seen the CPU -- what else?

• Memory• Main/system memory• Specialist memory

• Peripherals• Keyboard, monitor, mouse• Drives (floppy, hard, pen)• Printers, scanners, fish-tank aerators

Memory (hum Cats tune)Memory (hum Cats tune)

• RAM (Random Access Memory)• can both read from and write to• used for main system storage, typically multiple

gigabytes (Gb) at this point• cost varies with retrieval speed (and size)

• Cache [“cash”] memory• extremely high speed memory, very expensive,

but used as part of CPU for performance

Losing my memoriesLosing my memories

• Problem with RAM -- requires continuous power.• DRAM -- “Dynamic” RAM• SRAM -- “Static” RAM is misnamed

• ROM (Read-Only Memory)• cannot be written (like CD-ROM!)• never loses data, even when power goes out• memory values built-in at factory

Programming ROMsProgramming ROMs

• ROM -- programmed at factory• build an explicit one or zero circuit, repeat

• PROM (Programmable ROM)• field-programmable by blowing fuses• problem : can’t “unblow” fuses (write once)

• EEPROM (Electrically Erasable PROM)• field-(re)programmable, but limited cycles

Buses and PortsBuses and Ports

• CPU is connected to memory via “bus,” a collection of wires

• Typical computer has 32-bit bus, meaning 32 data wires

• Buses also connect to “ports,” electrical sockets for peripheral connections

• “Peripherals” connect through ports or (internally) direct to bus

PeripheralsPeripherals

• Computers are useless if they can’t communicate

• Data input devices

• Data output devices

• Data storage devices

• Manipulative devices• and whatever else your imaginations can dream

up. Go wild -- it may be worth $$$

Input devicesInput devices

• Keyboard

• Pointing devices• mouse, TrackPoint, touchpad, trackball

• Readers• bar-code readers, document scanners, light pens

• Cameras

• Phone interfaces

Output devicesOutput devices

• Video screen/monitor

• Printer

• Sound card/speaker

Storage devicesStorage devices

• Hard drives

• Floppy drives

• ZIP drives

• Pen drives

• CD/DVD drives

• Magnetic tape

Optical drivesOptical drives

• Metallic surface has lots of little pits

• Disk rotates at very high speed

• Read by laser beam; 32x drives has 32

• CD-RW use more powerful laser to burn crystal surface, changing reflectivity

• DVD has much more capacity than CD because pits are closer (and speed is faster)

Most important peripheralMost important peripheral

• The network card

• … or the cable modem, wireless card, etc.

• This needs a lecture all to itself

Choosing hardwareChoosing hardware

• New computers very expensive (Moore’s law, remember?)

• New computers not reliable

• Old computers may be obsolete or not supported any more

• Pg. 93 of textbook lists 9 C’s of criteria

• Rule of thumb: Buy what you need today.