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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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 $$$

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

9. Output devices • Video screen/monitor • Printer • Sound card/speaker

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

11. 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)

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

13. 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.