IRQ's

HOW A MODEM OPERATES

MODULATION

DEMODULATION

DIGITAL
(BINARY)

ANALOG
(TONES)

PHONE
LINE

ANALOG
(TONES)

DIGITAL
(BINARY)

     IRQ 0            System Timer
     IRQ 1            Keyboard
     IRQ 2            Cascade to IRQ 9
     IRQ 3            Com 2&4 (mouse)
     IRQ 4            Com 1&3 (modem)
     IRQ 5            LPT 2 (but usually Sound Card )
     IRQ 6            Floppy drive
     IRQ 7            LPT Port 1 (Printer)
     IRQ 8            Real time clock
     IRQ 9            VGA, NIC (redirect to IRQ 2)
     IRQ 10           CD ROM Drive
     IRQ 11           Open
     IRQ 12           Open (Bus mouse port)
     IRQ 13           Math co-processor
     IRQ 14           IDE Controller (hard disk drive)
     IRQ 15           PCI/ISA Bridge (motherboard)PCI/ISA Bridge (motherboard

I/O ADDRESS's
COM1	3F8H
COM2	2F8H
COM3	3E8H
COM4	2E8H
LPT1	378h
LPT2	278h
Hard disk controller	1F0H

DMA's
DMA	DEVICE
0	AVAILABLE
1	AVAILABLE
2	FLOPPY DRIVE
3	AVAILABLE
4	2nd DMA CONTROLLER
5	AVAILABLE
6	AVAILABLE
7	AVAILABLE

BINARY NUMBERS
MOST SIG.							LEAST SIG.
128	64	32	16	8	4	2	1

LOGICAL MEMORY MAP
Expanded Memory	Uses virtual memory	Uses bank-switching to page data in and out of Upper memory quickly.
Extended Memory	1088k - end of memory	Was created for DOS applications to be able to access RAM outside of the first 640k.
High Memory Area	1024k - 1088k.	Reserved for use by single application or utility.
Upper Memory 640k-1024k	960k - 1024k.	Motherboard BIOS
	768k - 960k.	BIOS and RAM Buffers
	768k - 832k.	Used for Page Frames when Expanded memory driver is loaded
	640k - 768k.	Video RAM
Conventional Memory	1k-640k.	Used for DOS applications and TSR's

PHYSICAL MEMORY TYPES
SRAM	Static random access memory	Older type of ram. Uses transistors to store information
DRAM	Dynamic random access memory	Uses capacitors to store memory.Requires refresh
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.
WRAM	Windows RAM	Specialized memory for Windows accelerator cards, faster than normal VRAM, can be read from or written to simultaneously. (Dual-Ported memory)
CACHE MEMORY	memory used to cache CPU instructions	L1 cache located on CPU. L2 cache is external cache, located on motherboard.

POST ERROR CODES

BEEP CODES	PROBLEM
No beep ,system dead	Power supply dead, not plugged in
Countinuous beeps	Power supply bad or not plugged in correctly to motherboard, or keyboard stuck.
Repeating short beeps	Power supply may be bad
1 short beep nothing on screen	Video card failure
1 short beep, video present but system won't boot	Bad floppy drive, cable or controller
1 short beep, video present, system boots	Normal operations
2 short beeps	Configuration error
1 long beep, 1 short beep	System board bad
1 long beep, 2 short beeps	Video card failure

NUMBER CODES	PROBLEM
Series 1 * *	Any series 1 * * are related to system board problem
161	CMOS battery failure
164	Memory size error, usually following a memory upgrade (Run BIOS setup to recognize the new memory)
Series 2 * *	Any series 2 * * indicates a memory related problem.
201	Memory test failed, 1 or more portions of RAM were found to be bad
Series 3 * *	Any series 3 * * usually indicate keyboard problem
Series 4 * *	Monochrome video problems
Series 5 * *	Color video problems
Series 6 * *	Floppy disk system problems
Series 17 * *	Hard disk problem or hard disk controller

CPU TYPES
CPU (YEAR)	COMMENTS TRANSISTORS	EXTERNAL CLOCK SPEED	INTERNAL CLOCK SPEED	EXTERNAL BUS	INTERNAL BUS	INTERNAL CACHE
8086 (1978)	FIRST CPU	5 MHz	5 MHz	16 bit	16 bit	NO
8088 (1979)	USED IN FIRST IBM PC 29,000 transistors	8 MHz	8 MHz	8 BIT	16 BIT	NO
80286 (1982)	INTRODUCED THE IDEA OF PROTECTED MODE 134,000 TRANSISTORS	8,10, 12 MHz	8,10, 12 MHz	16 BIT	16 BIT	NO
80386DX (1985)	CAN SWITCH BETWEEN REAL AND PROTECTED MODE. FIRST 32 BIT CPU 275000 TRANSISTORS	16,20, 25,33 MHz	16,20, 25,33 MHz	32 BIT	32BIT	NO
80386SX (1988)	CHEAPER VERSION OF 386	16,20, 25,33 MHz	16,20, 25,33 MHz	16 BIT	32 BIT	NO
80486DX (1989)	INTODUCED INTERNAL L1 CACHE, BUILT-IN MATH COPROCESSOR 1.2 MILLION TRANSISTORS	25,33, 50 MHz	25,33, 50 MHz	32 BIT	32 BIT	8 K
80486SX (1991)	SAME AS 486DX EXCEPT WITH DISABLED MATH COPROCESSOR 1.1 MILLION TRANSISTORS	25,33, 50 MHz	25,33, 50 MHz	32 BIT	32 BIT	8 K
80486DX2 (1992)	CAN EXECUTE INSTRUCTIONS IN ONE CYCLE RATHER THAN 2 CYCLES IN DX 2.0 MILLION TRANSISTORS	25,33 MHz	50,66 MHz	32 BIT	32 BIT	8 K
80486DX4 (1994)	RUNS AT THREE TIMES THE SPEED OF THE MOTHERBOARD 2.5 MILLION TRANSISTORS	25,33 MHz	75,100 MHz	32 BIT	32 BIT	8 K
PENTIUM (1993)	CAN EXECUTE 2 INSTRUCTIONS AT A TIME USING SUPERSCALOR TECHNOLOGY 3.1 MILLION TRANSISTORS	60,66 MHz	60,66, 90,100, 133,150, 166,200 MHz	32 BIT	64 BIT	16 K
PENTIUM MMX (1996)	57 MORE INSTRUCTIONS TO HELP HANDLE VIDEO AND GRAPHICS	60, 66 MHz	60,66, 90,100, 133,150, 166,200 MHz	32 BIT	64 BIT	16 K
PENTIUM PRO (1996)	SPECULATIVE EXECUTION, DATA FLOW ANALYSIS 5.5 MILLION TRANSISTORS	66 MHz	180,200 MHz	32 BIT	64 BIT	16 K
PENTIUM II (1997)	USES PROPRIETARY SOCKET DESIGN - 242 SINGLE EDGE CONNECTOR 7.5 MILLION TRANSISTORS	66,100 MHz	233,266, 300,333, 350,366, 400,450 MHz	64 BIT	64 BIT	16K

BUS / EXPANSION CARD TYPES
BUS TYPE	BUS WIDTH	MAX SPEED	BUS MASTERING	COMMENTS CONFIGURATION
8-BIT	8-BIT	4.77 MHz	NO	No longer used, Configured by Jumpers and DIP Switches
ISA	16-BIT	8MHz or 10MHz (TURBO)	NO	Configured by Jumpers and Dip switches, Some are software configurable
EISA	32-BIT	8MHz	YES	EISA are backwards compatible with ISA. Software-"EISA Configuration Disk" or by Jumpers.
MCA	16-BIT or 32-BIT	10MHz	YES	Proprietary IBM design. Software - "Reference Disk", No longer used.
VESA or VL-BUS	32-BIT	PROCESSOR SPEED	YES	Backward compatible to ISA cards. Configuration with Jumpers.
AGP	32-BIT	PROCESSOR SPEED	~	Used in Video cards
PCI	32-BIT or 64-BIT	PROCESSOR SPEED	YES	Software configured - Plug & Play
PCMCI (PC-CARD)	16-BIT	33 MHz	NO	USED IN LAPTOPS, Some are software configured, some are Plug & Play
				Type 1	3.3mm thick	Memory upgrades
				Type 2	5mm thick	Modem and Network cards
				Type 3	10.5mm thick	Hard Drives

INTERFACE CABLES
FLOPPY DRIVE CABLE	34 PINS
FLOPPY PIN 34 = CHANGE SIGNAL
ST-506	20 WIRE RIBBON (DATA) 34 WIRE RIBBON (CONTROL)
IDE/EIDE DRIVE CABLE	40 PINS
SCSI DRIVE CABLE	50 PINS
SCSI ULTRA-WIDE	68 PINS

SCSI ID #
8-BIT
0	BOOTABLE DRIVE
7	CONTROLLER
2-6	AVAILABLE
16-BIT
0	BOOTABLE DRIVE
15	CONTROLLER
2-15	AVAILABLE

MODEM COMMANDS
COMMAND	FUNCTION
ATA	ANSWER
ATD	DIAL
ATDL	REDIAL
ATF1	HALF-DUPLEX OFF
ATHN	HANG UP
ATMN	SPEAKER ON/OFF
ATSR	DISPLAY REGISTER
ATH	HANGS UP MODEM

O S I / R M
LAYER #	LAYER NAME	PROTOCOLS USED	DESCRIPTION COMMENTS
7	APPLICATION LAYER	SMTP BOOTP FTP HTTP AFP SNMP SMB X.500 NCP NFS Telnet Gopher	User interface, supports file transfer and network management, controls data flow and error recovery.
6	PRESENTATION LAYER		Determines the "format" of the data, network security, and file transfers. Data translation and encryption are handled at this layer.
5	SESSION LAYER		Establishes, manages and terminates network sessions, enables network procedures such as identifying passwords, logons and traffic flow.
4	TRANSPORT LAYER	TCP SPX NWLink ATP NetBEUI	Provides error-checking and reliable end-to-end communication, supports end-to-end error recovery and data flow control.
3	NETWORK LAYER	IP IPX NWLink DDP NetBEUI X.25 Ethernet	Organizes data into "datagrams" or packets, addresses messages and translates logical names and addresses into physical addresses, determines best data path based on network conditions.
2	DATA LINK LAYER		Provides reliable data transfer across the physical link, prepares the information so it can be placed on the transmission medium.
1	PHYSICAL LAYER		Describes how data is transmitted over the physical medium. Defines how long each piece of data is and the translation of eachninto electrical pulses that are sent over the wire. It also relates electrical, optical, mechanical and functional interfaces to the cable.

MONITOR REFERENCE TABLE
ADAPTER	RESOLUTION	COLORS
MDA (Monochrome Display Adapter)	720x350	2
CGA (Color Graphics Adapter)	320x200	4
CGA (Color Graphics Adapter)	640x200	2
EGA (Enhanced Graphics Adapter)	640x350	16
VGA (Video Graphics Adapter)	640x480	16
VGA (Video Graphics Adapter)	320x200	256
SVGA (Super VGA)	640x480	65,536
	600x800	256
	1024x768	16
XGA (Extended Graphics Array)	600x800	65,536
XGA (Extended Graphics Array)	1024x768	256

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.
PAGE PRINTERS
EP LASER	The drum is scraped and exposed to a flourescent lamp for cleaning. A charging corona places a strong negative(-600Vdc) charge onto a photosensitive drum and uses a laser to paint an image onto the drum reducing image areas to(-100Vdc), toner is attracted to the drum from the developing roller in the toner cartridge. The image is then transferred to the paper at it's line of contact by means of a corona wire(+600Vdc). A static elimenator removes the remaining charge from the paper. the paper and toner then go into the fuser where they are pressed and heated to 350'F. The paper with the final image is rolled out of the printer.
HP LASER	The drum is scraped and exposed to LED's for cleaning. A charging roller places a strong negative(-600Vdc) charge onto a photosensitive drum and uses a laser to paint an image onto the drum reducing image areas to(0Vdc), toner is attracted to the drum from the developing roller in the toner cartridge. The image is then transferred to the paper at it's line of contact by means of a transfer roller(+600Vdc). A static elimenator removes the remaining charge from the paper. The paper and toner then go into the fuser where they are pressed and heated to 180'F. The paper with the final image is rolled out of the printer.
LED	Same as HP and EP except drum and toner cartridge are separate and the image is written to the drum with LED's (Light Emitting Diodes).

LASER PRINTERS
STEP	PROCESS	DESCRIPTION
1	CLEANING	EP drum is cleaned with a rubber blade , and the eraser lamp (or LED's) are turned on near the surface of the EP drum, causing the drum to loose it's charge. Now the drum is ready to take on a new image
2	CONDITIONING ( CHARGING )	The EP drum is given a negative charge of approximately -600 Volts by the primary corona wire
3	WRITING ( EXPOSING )	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.
4	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.
5	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.
6	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 off the paper by the cleaning pad.
~	END OF CYCLE	The paper with the final image is rolled out of the printer.
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 can also be caused by the bad separator pad.

LASER PRINTER ERROR CODES
00 Ready	Printer is in stand-by mode and ready to print .
02 Warm up	The fuser is being warmed up before the Ready state.
05 Self-Test	Full self test has been initiated from the front panel.
11 Paper Out	The paper tray sensor is reporting that there is no paper in the paper tray.
13 Paper Jam	A piece of paper is caught in the paper path.
14 No EP Cart	There is no EP toner cartridge installed.
15 Engine Test	An engine self-test is in progress.
16 Toner Low	The toner cartridge is almost empty. Replacement will be necessary soon.
50 Service	A fuser error has occurred, possibly a fuser lamp failure.
51 Error	Laser scanner assembly problem.
52 Error	The scanning motor in the laser scanning assembly is malfunctioning.
55 Error	Communication problem between formatter and DC controller.
* In the case with most of these errors the printer will not print as long as the error exists. *

TYPES OF CONNECTORS
CONNECTOR	# OF PINS / SOCKETS	MALE or FEMALE	COMMON APPLICATIONS
DB-9	9 PINS	MALE	SERIAL PORT
DB-9	9 SOCKETS	FEMALE	EGA/CGA VIDEO PORT, TOKEN RING ADAPTER PORT
DB-15	15 SOCKETS	FEMALE	3 ROWS/5 VGA/SVGA VIDEO ADAPTER 1 ROW/7,1ROW/8 MIDI OR NETWORK
DB-25	25-PINS	MALE	SERIAL PORT
DB-25	25 SOCKETS	FEMALE	PROBABLY A PARALLEL PORT or EXTERNAL SCSI BUS
RJ-11	4 PINS	MALE	TELEPHONE WALL JACK
RJ-12	4 PINS	MALE	TELEPHONE HANDSET CORD
RJ-45	8 PINS	MALE	10Base-T ETHERNET CABLE
CENTRONICS-36	36 PINS	MALE	PARALLEL CABLE
CENTRONICS-50	50 PINS	MALE	SCSI CONNECTOR
CENTRONICS-50 HP	50 PINS	MALE	SCSI CONNECTOR
CENTRONICS-68	68 PINS	MALE	SCSI CONNECTOR
DIN-6	6 SOCKETS	FEMALE	PS/2 MOUSE PORT
DIN-8	8 SOCKETS	FEMALE	MAC PRINTER
DIN-9	9 SOCKETS	FEMALE	BUS MOUSE PORT
BNC-T	~	~	Co-axial cable (Thinnet)
AUI	~	~	Co-axial caple (Thicknet)

TYPES OF CABLES
CABLE TYPE	CONNECTORS	MAX LENGTH
NULL MODEM	DB-9F ,DB-9F	25 FEET
NULL MODEM	DB-25F , DB-25F	25 FEET
RS-232 (MODEM CABLE)	DB-9F , DB-25M	25 FEET
RS-232 (MODEM CABLE)	DB-25F , DB-25M	25 FEET
PARALLEL PRINTER	DB-25M , CENTRONICS 36	10 FEET
EXTERNAL SCSI	MALE CENTRONICS-50 MALE CENTRONICS-50	10 FEET (TOTAL SCSI BUS LENGTH)
VGA CABLE	DB-15M , DB-15M	3 FEET
NETWORKING CABLES
TWISTED PAIR	RJ-45	100 METERS
CO-AXIAL RG-58 THINNET	BNC-T	185 METERS
CO-AXIAL RG-59 THICKNET	AUI	500 METERS