Kenwood Sale!!!!
MAKE $$ on GOOGLE! I do!
Sign up for PeoplePC
Online now!
HIGH-SPEED For LESS
Web Page Analyzer (FREE)
Pride- Have
some!
Please support our sponsors that help to keep this free...
Some DNFTechTips© for you aspiring A+ Techs
Please feel free to print these out.
Here is an Easy way to remember your IRQ's. Just memorize the saying and you should have no problems come test time.
| 00 | Sam | System Timer |
| 01 | keeps | Keyboard |
| 02 | Viagra | Video adapter |
| 03 | Capsules | Com 2, 4 |
| 04 | Close | Com 1, 3 |
| 05 | Especially Empty | (LPT2 or Sound card) |
| 06 | For | Floppy |
| 07 | Late | LPT1 |
| 08 | Time | Real time clock |
| 09 | Classes | Cascaded IRQ2 |
| 10 | Every | Empty |
| 11 | Even | Empty |
| 12 | Monday | Mouse |
| 13 | Except | Empty (Math Coprocessor) |
| 14 | Holiday | Hard Drive Controller |
| 15 | Evenings | Empty(2nd HD Controller) |
A quick tip for remembering DMA Addresses
List down Com1, com2, Com3, Com4 LPT1, and LPT2. In the next column Alternate 3
and 2. In the last column do 2 each of F,E,and 7. The add 8 to the end of each
number.
It should look like this:
Com1 3f8
Com2 2f8
Com3 3e8
Com4 2e8
LPT1 378
LPT2 278
For ESD - remember: When it is cold and dry, static is
High
| There are 16 IRQ's: 0 through 15. there is no such thing as IRQ 16 and higher. IRQ is a signal that a device sends to CPU to request it's attention.
|
 |
Donate $2.00 to our FREE Tech Guide page editors for their time and get $5.00 for new user signup |
| IRQ # | Device |
| 0 | System timer |
| 1 | Keyboard |
| 2 | Cascade to IRQ9. Can't be used. |
| 3 | Com ports 2 and 4 |
| 4 | Com ports 1 and 3 |
| 5 | Usually available. Sometimes LPT2. Most often used for sound cards. |
| 6 | Floppy drive |
| 7 | LPT1 |
| 8 | Real time clock |
| 9 | Video display adapter |
| 10 | Available |
| 11 | Available. SCSI adapter will usually use this IRQ. |
| 12 | Available or PS2 mouse |
| 13 | Math coprocessor. |
| 14 | Primary IDE controller |
| 15 | Secondary IDE controller. If there is no secondary IDE controller on the board, or secondary IDE controller is disabled in CMOS, IRQ 15 is available |
Memorize your DMA channels. DMA stands for direct memory access and allows a device to access the RAM directly, bypassing the CPU. Only one DMA channel can be assigned to one device. Most systems today have 2 DMA controllers and 8 DMA channels 0 through 7. There is no DMA 8
| DMA | Device |
| 0 | Available |
| 1 | Available |
| 2 | Floppy drive |
| 3 | Available |
| 4 | 2nd DMA controller |
| 5 | Available |
| 6 | Available |
| 7 | Available |
You need to remember the base memory addresses for communication ports.
| Port | Base address |
| COM1 | h3F8 |
| COM2 | h2F8 |
| COM3 | h3E8 |
| COM4 | h2E8 |
| LPT1 | h378 |
| LPT2 | h278 |
CPU TYPES
Memorize the types of CPUs. The exam does not go into details of what year certain CPU first came out, but you need to know what CPU introduced the real mode and what CPU has the coprocessor disabled.
| CPU | Comment | Model year | External clock in MHz |
Internal clock in MHz |
Can access memory up to | Internal cache | Built in co-processor (FPU) |
Internal bus | External bus |
| 8086 | First CPU | 1978 | 5 | 5 | 1 Mb | no | no | 16 bit | 16 bit |
| 8088 | Used in the first IBM PC/XT computer. 29000 transistors. | 1979 | 8 | 8 | 1 Mb | no | no | 16 bit | 8 bit |
| 80286 | Introduced the idea of protected mode. 134000 transistors. | 1982 | 8,10,or 12 | 8,10,or 12 | 16 Mb | no | no | 16 bit | 16 bit |
| 80386DX | Can switch between real and protected mode. First true 32 bit CPU. 275000 transistors. | 1985 | 16,20, 25,33 |
16,20, 25,33 |
4 Gb | no | no | 32 bit | 32 bit |
| 80386SX | Cheaper version of 386 known as derivative chip | 1988 | same as 80386DX | same as 80386DX | 16 Mb | no | no | 32 bit | 16 bit |
| 80486DX | Introduced internal L1 cache. About twice as fast as 386. 1.2 Million transistors | 1989 | 25,33,50 | 25,33,50 | 4 Gb | 8 K | Yes | 32 bit | 32 bit |
| 80486SX | Same as 486 but with disabled co-processor | 1991 | same as 486DX | same as 486DX | same as 486DX | same as 486DX | NO | same as 486DX |
same as 486DX |
| 80486DX2 | Can execute instruction in one cycle rather than 2 cycles in DX | 1992 | 25, 33 | 50, 66 | 4 Gb | 8 K | Yes | 32 bit | 32 bit |
| 80486DX4 | Runs at 3 times the speed of motherboard | 1994 | 25, 33 | 75, 100 | 4 Gb | 8 K | Yes | 32 bit | 32 bit |
| Pentium | 64 bit data bus. Can execute 2 instructions at the same time by using superscaler technology. 2 internal 8K cache chips. Cache controller built on board. 3.1 million transistors | 1993 | 60 or 66 | 60, 66, 90, 100, 133, 150, 166, 200 | 4 Gb | 16 K | yes | 64 bit | 32 bit |
| Pentium MMX | 57 additional instructions to better handle video and graphics. Improves performance in multimedia applications 50 - 100 %. To utilize MMX technology programs must be written to use MMX instructions. | 1996 | same as Pentium | same as Pentium | same as Pentium | same as Pentium | same as Pentium | same as Pentium | same as Pentium |
| Pentium PRO | Speculative execution, Dataflow analysis. 5.5 million transistors. | 1996 | 66 | 180, 200 | 64 bit | 32 bit | |||
| Pentium II | Uses proprietary socket design - 242 SEC slot (Single Edge Connector) L2 cache built in the cartridge. 7.5 million transistors. | 1997 | 66, 100 | 233, 266, 300, 333, 350, 366, 400, 450 | 4 Gb | 16 K | Yes | 64 bit | 64 bit |
| Pentium III | Not covered on the exam | 1999 | 100 | 500, 550 |
MOTHERBOARDS/ BUS TYPES/ MEMORY
There are 2 basic types of motherboards: XT - extended technologies and AT - advance technology. ATX and baby AT are modifications of an AT format. All Pentium II motherboards are ATX format. A characteristic of an ATX format is that the computer can be shut down by software. Modern motherboards have 2 - 3 ISA, 3 - 4 PCI and 1 AGP expansion slots. Some motherboards have built in sound card, some have built in SCSI card. Motherboard configuration is stored in BIOS.
Expansion cards/external bus types
| Bus type | Data bus width | Speed | Comments | . | |
| 8 bit card | 8 bit | 8 MHz | on of the first expansion cards. Not used in modern computers | . | |
| ISA | 16 bit | 8 MHz | Still in use today. Configuration is done by setting jumpers | . | |
| EISA | 32 bit | 8 MHz | EISA bus slots are backward compatible with ISA cards. EISA cards can be configured by software or by jumpers. | . | |
| VESA or VL-bus | 32 bit | Speed of Processor | Backward compatible with ISA cards. Configuration is done by setting jumpers. Most often used for video cards. | . | |
| PCI | 64 bit and 32 bit | Speed of Processor | Plug and Play cards. |  |
|
| AGP | 32 bit | Speed of processor | Used in video cards. | . | |
| MCA | 16 bit and 32 bit | 10 MHz | Configured by software. Proprietary IBM design. Not used in modern computers. | . | |
| PCMCIA (PC card) | 16 bit | 33 MHz | Used in laptop computers. Some are plug and play, some software configured. There are 3 types of PC cards | Type 1: 3.3 mm thick. Used for memory upgrade cards. |
 |
| Type 2: 5 mm thick. Modem and network cards. Some are combination Modem/NIC cards. | |||||
| Type 3: 10.5 mm thick. Used in PC card hard drives. | |||||
|
Hard drives.
Low level formatting is done at the factory. It organizes the hard drive into tracks and sectors. It's possible to do a low level format on the drive but not recommended. To prepare the hard drive for installation of the operating system, you must first create a partition and set it as an active partition. Boot up with a DOS boot disk and use FDISK command to create partitions. Hard drive can have 3 primary and 1 extended partition. Extended partition can be deviled into up to 23 logical partitions. Typical IDE drive supports up to 528 Mb of storage. EIDE drive supports 2gb and larger partitions. A modern motherboard has 2 HDD controllers, each supports 2 devices. When installing a second hard drive, set the jumper on it as a slave drive and the jumper on the first drive as a master drive. To improve performance, choose the faster drive to be a master drive. If you only have 2 IDE devices like hard drive and CD ROM, you can disable a secondary controller in BIOS to free up an IRQ and to speed up the boot process. If you need to have more then 4 devices, you must use SCSI devices with a SCSI card. SCSI cards can be SCSI 1, SCSI 2, and SCSI 3 (ultra SCSI). SCSI 1 supports up to 8 devises including the SCSI card. The devices in a SCSI chain must have unique SCSI IDs. SCSI card typically have ID7. SCSI 2 is a more popular adapter and supports up to 16 devices, also has higher transfer speed. Modern SCSI cards a combination SCSI2/SCSI3 cards. Internal SCSI cable is a 50 pin ribbon cable (not compatible with SCSI 3 devices). External SCSI cable is a shielded cable with Centronics-50 or female DB-25 connector. If the question on the exam does not mention what category a SCSI adapter is, assume they are talking about category 1 ( 8 devices ). The SCSI chain must have terminators at both ends. Terminators are resistors. SCSI card usually has a built in terminator. SCSI hard drives are more expensive than EIDE hard drives but offer higher access speed. Memory.
The first 1024Kb of ram represents DOS memory model. Memory above the first 1024K is called Extended memory. The first 64K of extended memory is called high memory.
|
| Upper memory (reserved memory) | 960KB - 1024KB | Motherboard bios | |
| 768KB - 960KB | Bios and Ram buffers | First 64KB of this memory can be used for page frames when Expanded memory driver is loaded. | |
| 640KB - 768KB | Video ram | ||
| Conventional memory | 0 - 640KB | Conventional memory | Used to load DOS (in first 64KB), run programs, load drivers, TSRs |
Types of memory.
| SRAM | Static random access memory | Older type of ram. Uses transistors to store information |
| DRAM | Dynamic random access memory | Uses capacitors to store memory. |
| ROM | Read only memory | Data in ROM can not be erased or changed |
| PROM | Programmable ROM | After the data is programmed into ROM, it can't be erased or changed |
| EPROM | Erasable PROM | Data can be erased by shining special ultraviolet light through a small window on the chip. The chip can then be reprogrammed. |
| EEPROM | Electronically erasable PROM | Data can be erased by sending a special electric charge. Chip can then be reprogrammed. Modern computers use EEPROM to store BIOS. |
| VRAM | video ram | Special type of ram used on video cards. |
| Cache memory | memory used to cache CPU instructions | L1 cache located on CPU. L2 cache is external cache, located on motherboard. |
PRINTERS
2-4 questions on the exam will be about laser printers. Those are easy if you remember how laser printers work. 2-4 questions will be about other type of printers like bubble jet, ink jet and dot matrix.
Laser printers
| Process | Description | |
| 1 | Cleaning | EP drum is cleaned with a rubber blade before it can take on a new image |
| 2 | Conditioning | The EP drum is given a negative charge of approximately -600 Volts by the primary corona wire |
| 2 | Writing | A laser beam is used to write to the EP drum, causing the dots on the drum to loose some of the negative charge and become relatively positively charged. |
| 3 | Developing | A toner is transferred from the toner cylinder to the EP drum by attracting to the area of the drum that has relative positive charge. |
| 4 | Transferring | The transfer corona wire charges the paper with a high positive charge. The EP drum turns as the paper passes under It, pulling the toner into the paper. A static charge eliminator prevents the paper from wrapping around the drum. |
| 5 | Fusing | The paper passes between the heated fuser roller and the rubber roller, the toner is melted and pressed into the paper. The heated roller reaches the temperature of about 180 degrees Celsius. The temperature sensor on the fuser roller will shut down the printer if the temperature gets dangerously high. Finally the excess toner is scrubbed of the paper by the cleaning pad |
| 6 | End of cycle | The paper with the final image is rolled out of printer. The eraser lamp is turned on near the surface of the EP drum, causing the drum to loose it's charge. |
| The toner is a combination of plastic, metal and organic compounds. In most laser printers the toner and EP drum are contained in one "toner cartridge". Do not recycle the toner cartridge, it needs to be replaced. | ||
| A paper jam can occur when the wrong type of paper is used. It can cause more than one page to enter the registration rollers. A jam cam also be caused by the bad separator pad. | ||
Other printer types
| Type | Process | Comment |
| Daisy-wheel printer. | A computer version of an electronic type writer. | One of the first types of printers developed. Not used any more |
| Dot matrix (impact printer) | Combination of pins on the printhead hit the ribbon, causing it to leave the marks on the paper. Useful when you need to print carbon copies like receipts or shipping invoices. | Typical printhead has 9, 18, or 24 pins. Printhead becomes very hot. Don't touch it. Never lubricate a printhead. If the ribbon is too tight, the image can become smudged. Broken pins on the printhead will cause incomplete characters. |
| Ink Jet | Ink is pumped from the reservoir through a nozzle by a special pump. | Ink jet printers were messy and were replaced with bubble jet printers. |
| Bubble Jet | Ink cartridge contains ink, printhead and special piezoelectric crystal. When signal is send to the crystal, it expands, forcing the ink out. | Do not refill bubble jet printer cartridges. They need to be replaced. |
Cables
| Cable type | Connectors | Maximum length |
| Modem cable RS - 232 | DB-9F, DB-25M | 25 feet |
| Modem cable RS - 232 | DB-25F, DB-25M | 25 feet |
| Printer cable | DB-25M, Centronics 36 | 10 feet |
| External SCSI cable | Centronics 50M, Centronics 50M | 10 feet |
| VGA cable | DB-15M, DB-15M | 3 feet |
Display adapters/Monitors
| Adapter type | Resolution | Colors |
| XGA (extended graphics array) | 600X800 | 65,536 |
| 1024X768 | 256 | |
| SVGA (super VGA) | 640X480 | 65,536 |
| 600X800 | 256 | |
| 1024X768 | 16 | |
| CGA (color graphics adapter) | 320X200 | 4 |
| 640X200 | 2 | |
| EGA (enhanced graphics adapter) | 640X350 | 16 |
| VGA (video graphics adapter) | 640X480 | 16 |
| 320X200 | 256 |
Modems
Modems use asynchronous transmission. Digital modems use synchronous transmission. Digital modems are used to connect to ISDN lines.
| Modem commands | Command function |
| ATA | Answer |
| ATD | Dial |
| ATH | Hang up |
| ATZ | Reset |
Basic network terminology
| LAN | Local area network. Typical network inside an office or inside a building |
| MAN | Metropolitan area network. A network that connects several LANs in a city. |
| WAN | Wide area network. A network that spans over long distance. Internet is an example of WAN. |
| TOPOLOGY | A way to lay out a network. |
Preventive maintenance/Safety/Troubleshooting
Electrostatic discharge (ESD) can damage the component at as little as 80 volts. CMOS chips are most susceptible to ESD. Static electricity builds up more in cold and dry places. Use humidifiers to keep room humidity at 50% to prevent static build up.
When working on computers, use special ESD wrist strap. Do not use a piece of wire to ground yourself. An ESD wrist strap has built-in resistor to prevent electric shock. Use specially designed grounded ESD mats. Do not wear synthetic clothing. Place all electronic components into antistatic bags. Antistatic bags can be reused. Keep your workplace clean.
When repairing a monitor, do not wear an ESD wrist strap. The capacitor inside the monitor can retain high voltage charge.
To put out an electrical fire use type C extinguisher or multipurpose ABC type extinguisher.
Do not disassemble power supplies. They need to be replaced.
To clean a keyboard soak it in a distilled dematerialized water as soon as possible after the spill.
Clean the inside of the PC with compressed Air. Compressed Air do not create ESD.
A Multimeter can be used to test a fuse. A good fuse will show resistance of 0 ohms. A bad fuse will show infinity ohms. When testing an unknown source of electricity, set the Multimeter to the maximum voltage settings to avoid damaging the Multimeter.
If a light an a floppy drive stays on, reverse the floppy cable to solve the problem. (remember red is pin one)
Donate $2.00 to our FREE Tech Guide page editors for their time and get $5.00 for new user signup
;
How fast is YOUR internet connection???? <-click here !
This web page and web site has
been developed and is maintained exclusively by Frank Toms CEO of DNF
Technologies. As DNF modifies its products, programs, and policies, information
contained in this web site is subject to change. This web site is not authored,
sponsored or maintained by any of the product companies listed in these pages.
For information and comments relating to this page and or its content's see
below..
© 2002 All Rights Reserved.
DNF Web Designs.
(Graphic
Designs
by Amber )
Last modified 08/28/2004 10:32
This site developed using
2000
No part of this
web site may be reproduced, transmitted or stored in any form
or by any means,
electronic or mechanical, without prior written permission from
Copyright D&F/DNF Tech
© ™
2002
All Rights
Reserved.
Privacy Policy.
last updated
08/28/04 10:32 AM
FAMH and FAHM © ™ 2002 All Rights Reserved.