Memory and Peripherals COSC-100 (Elements of Computer Science) Prof. Juola

Basic 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) 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 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 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 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

Peripherals 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 devices Keyboard Pointing devices mouse, TrackPoint, touchpad, trackball Readers bar-code readers, document scanners, light pens Cameras Phone interfaces

Output devices Video screen/monitor Printer Sound card/speaker

Storage devices Hard drives Floppy drives ZIP drives Pen drives CD/DVD drives Magnetic tape

Optical 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 peripheral The network card … or the cable modem, wireless card, etc. This needs a lecture all to itself

Choosing 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.