ClassLan

Notes - 23 May

PC Peripherals

Hot Swappable
SCSI only, not IDE
Swap drives while the PC is still running (known as hot-swap)

Hot Pluggable
Plugging cable into a device and PC while the PC is still running - USB


Upgrading BIOS Follow the instructions
EEPROM (Electrically Erasable Programmable Read Only Memory) used in Flash-able ROMs (CMOS)


Laptop Power Sources

NiCad Nickel Cadmium
Subject to Memory Effect

NiMH Nickel Metal Hydride
Dose not suffer from Memory Effect
About 10% more power than NiCad
Only lasts for 400 charge cycles

LiON Lithium Ion
Does not suffer from Memory Effect
10% more power than NiCad
LiON requires that laptops have special control circuitry and they are more expensive than NiCad NiMH
Only lasts for 400 charge cycles


Fuel Cells A device that produces power from the electrochemical or catalytic breakdown of some chemical substance (usually hydrogen or hydrocarbon), with water vapour as the only emission


Modems

External Modem Use an existing serial port, so they don’t have the configuration problem with IRQs and I/O addresses.

UART (Universal Asynchronous Receiver/Transmitter)
The chip that manages the serial data that’s moving in and out through the serial port.
If the modem is 9600bps or faster, you need to use a 16-bit UART for example the 16450 or 16550 models
(16550 has a transfer rate of 115,200bps)

External Modem Lights
OH Off Hook Modem is dialing or has the phone off the hook
SD(TX) Transmit Data (Modem transmits)
RD(RS) Receive Data (Modem receives)
AA Auto Answer (Auto pick-up)
RTS Request to Send


Cable Modem Used to connect PCs and other devices to a cable television

DOCSIS (Data Over Cable Service Interface Specification)
Specifies how to allow data services over a cable system


COM PORTS IRQ Addresses I/O Address
COM 1 4 3F8-3FF
COM 2 3 2F8-2FF
COM 3 4 3E8-3EF
COM 4 3 2E8-2EF


PDA (Personal Digital Assistant)
The PDA must have a method of connecting to the PC, most often this is done through serial or USB
Also, pieces of software known as conduits facilitate the communication between software on the PC (like Outlook) and the apps on the PDA


UPS: Uninterruptible Power Supply
Replaces line power if interrupted with no break in supply
SPS: Standby Power Supply
Like a UPS but the ‘wall’ powers the PC directly

EMI: (Electromagnetic Interferrence)
Caused by the electrometic waves emmited in motors in appliances

RFI: (Radio Frequency Interference)
Higher-frequency version of EMI

Line Conditioners Devices used to clear up problems with EMI and RFI

Spike Power overage condition that lasts for an extremely short amount
of time

Surges The result of faulty transmission equipment at power stations or lighting strikes
Surges last longer than Spikes

Sag A momentary drop in voltage, lasting a few milliseconds

Brownout Occurs when voltage drops below 220v for a second or more

Blackout Occurs when power drops from 220v to 0v in a short time period


Optiming PC Performance

Air Cooling CFM (Cubic Feet Per Meter)
Liquid Cooling Achieves better cooling performance than Aip Cooling
Much more expensive than Air Cooling
Phase Cooling Change liquid to gas through 'Phase Change'
Achieves CPU temputures of -20C


Preventing ESD CMOS chip most likely to suffer from ESD
ESD perfers a cool and dry environment


Anstistatic Wrist Strap Uses a 1-megaohm rersistor to bleed charge away


Fire Safety Types of Fire Extingushor
A: Water-based extingushing material for wood and paper
B: Carbon Dixode for flammable liquids
C: for electrical fires
D: Metal powder or NaCl (Salt) for flammable metals like phosphorus and sodium


The monitor: Do not try to repair the monitor, but if you do, use
'High-Voltage Probe' that bleeds voltage


Cleaning Systems Clean a monitor with a damp cloth. Not cleaners
Clean a keyboard by soaking it in distilled water and drying it off therefor removing the impurities
Electronic connectors are cleaned by using a swab moistoned in distilled, denatured isopropyl alcohol
Use compressed air to clean the inside of PCs

posted by ClassLan @ 9:56 PM