Newbie Guides Beginners Corner PC Hardware Reference Part 2

The PC hardware reference guide is in three parts.

PC Hardware Reference Guide - Part 2

Tutorial Quick Links:
Installation, Configuration and Upgrading
Diagnosing and Troubleshooting
Safety and Preventative Maintenance
Part 2
Motherboard, Processors and Memory
Printers
Part 3
Portable Systems
DOS and Windows

Motherboard, Processors, Memory

This section is concerned with terminology and classifications of hardware.

CPU Chips:

• 8088 - Used an 8-bit bus and ran at 4.77MHz
• 386 - Could handle up to 16 MB of memory. 386SX had a 16bit data bus and operated at 16, 20, 25, and 33 MHz. 386DX had a 32bit data bus and operated at 16, 20, 25, and 33 MHz.
• 486 - Four types the SX, DX, DX2 and DX4. The bus for all is 32bit. An 8bit on chip cache was introduced also a Maths Co-Processor was in-build but disables on the SX.
• 586(Pentium Class) - 64bit data bus, 16bit cache. Combines two 486DX chips into one using the Dual Independent Bus Architecture resulting in true parallel processing. Heat sinks were required due to the large amount of heat generated.
• 686(Pentium II Class) - Integrated MMX technology. Uses Slot 1 instead of a socket.

Chip Characteristics

CPU	Size	V	Speed (MHz)	Heat Sink	Fan	Cache	Skts	Pins
8088		5	5 8	No	No	No	DIP	40
80286		5	6 10 12	No	No	No	LLC PGA PLCC	68
80386SX		5	16 20 25 33	No	No	No	PGA	100
80386DX		5	16 20 25 33	No	No	No	PGA	100
80486SX		5	16 20 25 33	No	Yes on 33 MHz	Write Through	PGA	100
80486DX		5	25 33 50	No	Yes on 33 MHz	Write Through	PGA SQFP	168 208
Pentium	1.95 x 1.95	2.9 3.3 5	60- 166	Yes	Yes	Write Back	PGA	296
Pentium Pro	2.46 2.66	2.9	233-266	Yes	Yes	Write Back	PGA	387

Bus Sizes of CPU's

Processor	Register	Data Bus	Address Bus
8088	16-bit	8-bit	20-bit
80286	16-bit	16-bit	24-bit
80386SX	16-bit	16-bit	24-bit
80386DX	32-bit	32-bit	32-bit
80486SX	32-bit	32-bit	32-bit
80486DX	32-bit	32-bit	32-bit
Pentium	64-bit	64-bit	32-bit

Random Access memory(RAM):

• Static RAM(SRAM) - SRAM doesn't have to be constantly refreshed. Uses a lot of power. Used in old IBM XT machines and was limited to 256K per chip.
• Dynamic RAM(DRAM) - DRAM use capacitors instead of transistors and switches. Needs constant refresh.
• Windows RAM(WRAM) - Specific to speed up graphical windows operations.
• Extended Data Output RAM(EDO RAM) - Has a cache on the chip and is 10-15% faster than DRAM. Requires a special motherboard.

Memory comes in 30 or 72 pin SIMMs or 168 pin DIMMS

Bus Architectures:

• Industry Standard Architecture(ISA) - This was introduced on AT computers. Allowed a 16-bit data bus. Used in 286 and 386SX PC's.
• Extended Industry Standard Architecture(EISA) - Introduced to compete against IBM's MCA. Uses a 32-bit data bus. Used in 386DX and 486 PC's.
• Peripheral Component Interconnect(PCI) - Designed to use Pentium Processors. Uses a 64-bit data bus. Uses a bridge circuit to be processor independent.
• Universal Serial Bus(USB) - A new technology for Plug and Play devices allowing up to 12 Mbps.
• VESA Local Bus(VL_Bus) - Used for Video cards on top of EISA.
• Personal Computer Memory Card International Association(PCMCIA) - Now called PC Card. Used in Laptops. Currently only 16-bit data bus.

Complimentary Metal-Oxide Semiconductor(CMOS)
The BIOS can only hold setting when the machine is on. Once it loses power it loses the settings. Upon re-boot these are loaded from CMOS which is powered by a battery.

Basic CMOS Settings:

• Printer Parallel Port
  • Unidirectional - Single direction communication.
  • Bi-directional Two directional communication. Used by HP printers.
  • ECP(Extended Capability Port) Same as Bi-directional but uses a DMA to bypass processor and speed up transfer.
  • EPP(Enhanced Parallel Port) Same as bi-directional and offers an extended control code set.
• COM/Serial Port
  • Memory Address Each COM port requires a unique memory address.
  • IRQ - Every COM port requires a unique IRQ to talk to the CPU.
  • COM1 = IRQ4 and 03F8
  • COM2 = IRQ3 and 02F8
• Hard Drives
  • Size - The Size is automatically detected by the computer.
• Primary Master/Secondary Slave
  • Each hard drive has a controller built in the drive that controls the drive.
  • If two drives were on the same channel the adapter could get confused.
  • By setting one as a master it tells it which is in charge.
• CDROMS
  • CDROMS on secondary channel alone are always set to slave.
  • Tracks - Each Ring.
  • Sector - Pie Slices.
  • Cylinder - Combination of identical tracks

Printers

This section explains the basic types of printers, concepts and how they work.

Types of Printers:
Daisy Wheel Printers
Uses impact method to imprint a character from a daisy wheel. Similar to a typewriter in operation. Excellent quality for text but no graphics. Uses a Ribbon

Dot Matrix Printers
Uses a matrix of pins to imprint an image. Uses a Ribbon. ROM programs the Fonts.

Bubble Jet Printers
Non Contact therefore quiet. Works by spraying ink onto the paper in a sequential fashion. Similar in operation to a dot matrix printer.

Laser Printers
Uses a Page Description Language (PDL) to print a page at a time. Main components are:

• Cleaning Blade - This rubber blade removes excess toner off the drum after the print process has completed.
• Photosensitive Drum - The core of the electrophotographic process. Involved in the six step EP process.
• Primary Corona Wire - Highly negatively charged wire erases the charge on the Photosensitive drum to make it ready for another image.
• Transfer Corona - A roller that contains a positively charged wire to pull the toner off the photosensitive drum and place it on the page.
• Toner - Plastic Resin. Naturally Negatively charged
• Fusing Rollers - Final stage of the EP process. Bonds the toner particles to prevent smearing. Uses heat to bond.

Electrophotographic Print Process(EP):
The process concerned with putting the image on the page. Follows Six processes.

1. Cleaning The Drum is cleaned and electrically erased.
2. Charging The Drum is negatively charged to 5000Vdc. Done by the Primary Corona.
3. Writing The Laser sweeps the length of the drum applying the image. The Laser reduces the negative charge on the drum where the image is going to be.
4. Developing The Toner is transferred to the area on the drum which has been swept by the laser.
5. Transferring - Once the image is on the drum the paper is fed through and the transfer corona wire attracts the image from the drum to the paper.
6. Fusing - The Fusing rollers heat up and pass the paper through bonding the toner to the paper. Uses a Non stick roller surface.

Troubleshooting:

• Blank Pages - Can be caused by No Toner, Transfer Corona Failure or HVPS Failure.
• Speckled Pages - Due to a failure in the cleaning step of the EP Process. Or a scratch on the EP drum.
• Ghosted Images - Caused if the erasure lamp doesn't erase all of the image from the EP drum before the next page is printed.
• Smudged Images - The fusing process must have failed. The heating elements in the fusing rollers may be faulty.
• Bubble Jet Printers - Never refill cartridges which are causing problems. The head is part of the cartridge so replace the entire cartridge.

These study notes were developed by Andrew Mason.

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