. Motherboard - main circuit board

1
Picture taken from Smart Computing January 1999 Vol. 10 Iss.1 pg 98

2. holds chips
* members.aol.com/wbox/power2.htm
o timing crystal which keep its thinking organized.
o Another timing crystal keeps track of the time and date.
+ Most computers also have a small rechargeable battery and an IC chip that keeps track of the time even when the main power switch is turned off.
+ timing crystal emits an electronic tick, tick, tick at a high rate of speed. The timing chip adds these ticks to the time and date. The battery keeps this going. Whenever the computer is turned on, the battery is recharged
3. most important chip = CPU
4. transistors
* basic building block of microprocessor
* electronic switches
o on - 1 - allows current to pass through
o off - 0 - does not allow current to pass through
5. connects expansion slots
* allow linking of peripheral devices to processor
* ISA slots - Industry Standard Architecture slots
* PCI slots - Peripheral Component Interconnect slots
6. connects ports
* method of attaching objects to peripheral card
o graphics card attaches to monitor
o printer plugs into a port
* AGP port - Accelerated Graphics Port
o transfer between processor and port at a rate of 500MBps
7. holds memory
* RAM - random access memory
* ROM - read only memory
8. Bus lines
* parallel electrical paths
o usually copper tracing motherboard
* transports data - electrical signals
* bus width
o amount of data able to be carried at one time
o number of electrical paths
o typically 8, 16, or 32 wires
o 16-bit bus has 16 wires.
o reference larger memory addresses
+ access more memory

9. Expansion slots and ports Smart Computing May 1998 vol9. iss 5

10. You can hook up lots of things to your PC
* hard drives
* tape backup machines
* scanners
* printers
* CD-ROM
* etc
11. Where to plug everything in?
12. Port
* allows access out of the computer for cables
* only a few normally available on computers
13. Solutions
* SCSI - Small Computer System Interface
o Devices are faster than EIDE (Enhanced Integrated Drive Electronics)
+ SCSI
+ SCSI-2
# Standard for scanners, printers, hard drives, etc
+ SCSI-3
# faster and more expensive than SCSI-2
+ Fast SCSI
# transfer data 10Mbps
+ Ultra SCSI
# transfer data 20Mbps
o more expensive
o little more difficult to set up?
o adapter card allows addition of 7-15 devices (depending on card)
+ internal or external
o daisy chain
+ SCSI bus
# data travels through path to adapter card.
# external hardware connected in series
# internal hardware connected to ribbon cable attached to adapter card
+ SCSI - under 20 feet
+ Fast SCSI - under 10 feet
o termination
+ Last device in chain must have terminator
# electrical resistor
# usually comes with devices
o to install a SCSI adapter card
+ remove cover of computer
+ locate a PCI slot
# Peripheral Component Interconnect
# Shorter slots usually white
+ remove cover strip on back that lines up with the slot
+ touch metal of computer to ground yourself
+ pick up host adapter
+ insert in PCI slot by gently rocking it back and forth until it clicks in place
o assign ID numbers to devices
+ used to be a dial on hardware
+ now may have software configuration
* Serial Solutions
o add Input/Output Expansion card
+ serial ports
# transfers data 1 bit at a time
# used primarily for mouse and modem
# sometimes called COM (communications) ports
+ parallel ports
# transfer data 8 bits at a time
# primarily printers and scanners
# sometimes called LPT (line printer terminal) ports
+ most computers have two COM and one LPT ports open
+ installing
# locate long black ISA slots (Industry Standard Architecture)
# unscrew metal plate in front of slot
# ground yourself
# pick up the card
# rock it in until it clicks
# restart computer and install device drivers or software that came with the card
o USB - Universal Serial Bus
+ USB automatically configures peripherals
+ Hot-swapping
# don't have to restart computer when change peripheral
+ attach 63 peripherals to single USB port
# daisy chain
+ installed in PCI slots
+ not compatible with Windows 3.1, or Windows 95 version A

14. Speed and Power
* most execute instruction in microsecond
o one-millionth of a second
* terminology
o millisecond - one-thousandth
o microsecond - one-millionth
o nanosecond - one-billionth
o picosecond - one-trillionth
* Speed usually expressed in megahertz (MHz)
o analagous to clock ticks
o millions of machine cycles per seconds
o 100MHz - capable of handling 100 million machine cycles per second
* Speed sometimes expressed in MIPS
o million of instructions per seconds
o .5 MIPS = 500,000 instructions per second
o more accurate than clock speed
+ some computers better at using each clock tick than others
* Speed sometimes expressed in megaflops
o million floating-point operations per second
o measures mathematical ability of computer
* Cache
o small block of very fast memory
o holds most frequently used data and instructions
+ designed for speeding up transfer of data or instructions
o internal cache - built right into processor
+ level 1 cache Smart Computing March 1998 vol 9 iss 3
o external cache - on seperate chips
+ level 2 cache Smart Computing March 1998 vol 9 iss 3
* Processor requests data or instructions

* first time retrieve from main memory - RAM
* next time - look first in cache
o transfer speed from cache much higher

* RAM - random access memory

* EDO RAM - extended data out RAM
o speeds measured in nanoseconds
* SIMM - single inline memory module
o plugs into motherboard
o contains memory chips
* SDRAM - static or dynamic ram
o works in synch with system clock
o faster than EDO RAM
* DIMM - dual inline memory module
o both sides of the card used for memory connections

* Coding Schemes

* ASCII
o 7 bits for a character
+ 2^7 = 128 unique combinations
+ always 0 bit in first spot of byte
o ASCII-8
+ 8 bits for a character
+ 2^8 or 256 unique combinations

* Architectures

* RISC - reduced instruction set computers
o small subset of instructions
+ MIPS vs MHz
* CISC - complex instruction set computers
o many are unused
+ unused instructions impediment to speed
+ more time to decode
* serial processing
o one instruction at a time
o pipe-lining instructions and data
+ previous action (fetch, decode, execute, store) doesn't have to finish before the next begins
* parallel processing
o use several processors at once