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More DNFTechTips©2000 for you aspiring A + Techs

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Acronyms:

SEC (Single Edge Connector)

SRAM (Static RAM)- does NOT need a constant refresh; Bulky and limited capacity

DRAM (Dynamic RAM)- uses charges in tiny capacitors; needs constant refresh.

ROM (Read Only Memory)- switches permanently manufactured in the on or off position.

DIP (Dual In-line Package)- individual RAM chips on very old PCs.

CMOS (Complimentary Metal Oxide Semiconductor)- BIOS settings are held here by the battery.

PROM (Programmable Read Only Memory)- memory that can be written to once.

EPROM (Erasable Programmable Read Only Memory)- exposure to UV light erases the chip.

PGA (Pin Grid Array)- this is the square CPU shape used by newer processors..

EEPROM (Electrically Erasable Programmable Read Only Memory)

IDE (Integrated Drive Electronics)- maximum of 528MB; Supports only 2 drives.

DMA (Direct Memory Address)- Devices that bypass the CPU and write directly to main memory reducing Cpu load..

ISA (Industry Standard Architecture)- 16bit data bus that operates at 8MHz.

MCA (Micro-Channel Architecture) IMB

CCD (Charge Coupled Device)

IEEE (Institute of Electrical and Electronics Engineers.)

ECP (Enhanced Capabilities Port)

EPP (Enhanced Parallel Port)

OSI (Open Systems Interconnection)

UTP- Unshielded Twisted Pair

STP- shielded Twisted Pair (Uses a braided foil shield around the twisted wires to decrease electrical interference).

CSMA/CD (sends data without checking network activity first).

CSMA/CA (Checks for network activity, sends a small amount of data, then sends actual data.

RSI (Repetitive Strain Injuries)

Connections:

RJ-11 (Phone Cord)

RJ-12 (Smaller, running from handset to phone)

RJ-45 (Standard Network twisted pair connector)

DB-25F (Probably null modem)

VGA (15pin)

PS/2 (6pin)

Printer Cable- 36pin centronics to DB-25 (Parallel cable).

Parallel Port- transfers data 8bits at a time (Data over 8 separate wires).

Definitions:

Power Surge- power overage condition that lasts several seconds.

Power Spike- power overage condition that lasts a few milliseconds at the most.

Clamping Speed- wow long it takes to go from the over-voltage volts to zero volts.

Clamping Voltage- the voltage the MOSFET shorts out.

Brownout- Voltage drops below 110 volts for a second or more.

Sequential- these are storage devices in which information must be fast forwarded to. (Ex: Tape Drive).

Flux transitions- HDDs use this process with an electromagnet to write to the platter.

Cylinder- the collection of tracks on all the platters.

Latency- Once the HDD head is in place, latency is how long until the data is moved under the head.

Bus Mastering- A process to allow devices to read/write to other devices directly.

Asynchronous- Transfer uses this order; Start bit/Data bit/Stop bit. Does not use clock ticks. (Serial Port).

Synchronous- Uses a clock tick to transfer information. Does not use start/stop bits.

Networks:

Topologies

	Bus; cheap and easy to install; Difficult to reconfigure and a break in the bus disables entire network.
	Star; cheap and easy to install, reconfigure, and fault tolerant; more expensive than bus.
	Ring; efficient and easy to install; Reconfiguration is difficult and expensive.
	Mesh; simplest and most fault tolerant; Reconfiguration extremely difficult, expensive and complex.
	Hybrid; gives combination of best features of each topology; Complex

Printers:

	Toner- toner is a black, carbon substance mixed with polyester resins and iron oxide; Includes print drum.
	Electric Stepper motor- an electric motor used in laser printers that can accurately move in small increments.
	Transfer Corona Assembly- charges the paper, which pulls the toner from the photosensitive drum.
	Static Charge Eliminator Strip- drains the charge from the paper so that it doesn't stick inside the printer.
	Fuser- Applies pressure and heat (350 degrees) to ensure that the toner stays on the paper.
	Printer Controller Circuitry- Uses a process called rasterizing to convert PC signals into device signals.
	Page description language- this is the language the printer uses to analyze how to print to the drum.
	Paper made from cotton is called Rag Stock.
	Basis weight or weight is how many pounds 500 sheets of 17"x22.5 weighs. (20lb paper is common).
	Caliper is the thickness of paper.
	ONLY use transparencies that are recommended for your printer; Otherwise the fuser will melt it.
	+600VDC is used to transfer the toner to the paper in an EP Laser Printer.
	Printer control circuitry forms the print job for the type of printer being used.
	In HPs, the laser discharges the paper to 0 volts. EP discharges to -100 volts.

Bus Types:

SCSI

	SCSI1; Original interface; centronics50 connector; 5MBps transfer rate; 8bit bus width.
	SCSI2; SCSI2 WIDE had an 8bit and 16bit bus width.
	SCSI2 FAST had 10MBps transfer rate.
	SCSI FAST-WIDE was fast and wide and transferred up to 40MBps.
	SCSI3; Standard not set yet.
	Ultra SCSI is a faster SCSI2 operating at 20MBps.

	8bit- 8bit; 4.77MHz
	ISA; 16bit; 8MHz (10 for Turbo)
	MCA; 16bit or 32bit; 10MHz
	EISA; 32bit;8MHz
	VL-BUS; 32bit; CPU speed
	PCI; 64bit; CPU speed
	PCMCIA; 16bit; 33MHz

Information:

Types of Laser Printers

	EP (Electro photographic)- Uses static charges, laser light, and toner. Process: Charging, Exposing, Developing, Transferring, Fusing, and Cleaning.
	HP (Hewlett Packard)- Very similar to EP Process. Process: Conditioning, Writing, Developing, Transferring, Fusing, and Cleaning.
	LED (Light Emitting Diode)- Uses LEDs held very close to the drum in place of the laser.
	Parallel interface- Transfers 8bits at a time over 8 wires.
	Standard; non bi-directional. 150KB/sec. Limited to 10 Feet.
	· Bi-directional; bi-directional parallel interface.
	Enhanced; greater Transfer speeds and can send memory addresses.
	ECP; designed to transfer Data at high speed to printers.
	EPP; supports bi-directional throughput from 150KB/sec to 1.5MB/sec.

There are four cabling methods

Coaxial Cable- consists of copper wire surrounded by insulation and a metal foil shield.
Fiber Optic Cable- provides transmission speeds from 100Mbps up to 1Gbps, a maximum distance of several miles, and is completely immune to electrical interference. This is used on networks that need long distances, extremely fast transmission rates, or have had problems with electrical interference.
Wireless- can use infrared light, laser light, narrow-band radio, microwave, or spread-spectrum radio.
Twisted Pair cable- UTP or STP; Maximum of 100 meters.

Category1 is for voice only transmissions; Used in most phone systems today.

Category2 is able to transmit data at 4Mbps; Consists of four twisted pairs.

Category3 is able to transmit data at 10Mbps; Consists of four twisted pairs with three twists per foot.

Category4 is able to transmit data at 16Mbps; Consists of four twisted pairs.

Category5 is able to transmit data at 100Mbps; It contains four twisted pairs of copper wire to give the most protection.

	The standard refresh cycle for monitors is 60Hz; some use 72Hz, which is of higher quality.
	Some SCSI devices don't use a physical terminator, but a DIP or jumper setting that terminates it.
	On PC SCSI, the higher the SCSI ID number, the higher the priority.
	Soft Memory Error- Single bit memory error that occurs with power fluctuations; Not reproducible.
	Hard Memory Error- Physical memory problems; reproducible.
	Parity is a form of error correction that assigns a 9th bit to the end of a binary number making the string odd or even.
	Never connect a laser printer to a UPS because they draw LARGE amounts of power.
	Line conditioners produce perfect power of 110V/60Hz.
	Power supplies carry lethal amounts of current and are not intended to be serviced.
	USB supports up to 127 devices simultaneously.
	A serial port transfers 1bit at a time at 57KB/sec and 50 feet maximum.
	Do not wear an Anti-Static wrist Strap when working on monitors.
	Learn resistor color codes.
	CPUs use the address bus to talk to a device; devices use the data bus to talk to the CPU.
	100 volts can damage a CMOS based IC.
	To measure resistance, the component must be removed from the board.
	Motorola manufactures Apple's CPUs.
	8080 was Intel's first PC CPU with 4.777MHz and 29,000 transistors.
	Intel stopped licensing its CPU designs with the 80386 CPU.
	Pentiums are completely 64-bit CPUs.
	MMX included 57 new instructions.
	External Bus (System Bus)- allows CPU to talk to another device (Expansion cards).
	Address Bus- Addresses memory locations.
	5 volts = a binary 1; 0 volts = a binary 0.
	16-bit buses use 16 wires to transmit data; 32-bit buses use 32 wires to transmit data.
	An advantage of using Dot Matrix printers is their compatibility with Carbon Paper.
	Modern mice use optical and opto-mechanical methods
	Key switched and capacitive are the 2 modern keyboards methods.
	The photo-sensitive drums and toner can be changed independently.
	Laser printers are called page printers because they print a page at a time.

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