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The PC

Hardware is physical; software instructs hardware what to do. Case protects and provides cool environment for other components. Form factor is a specific layout, shape and size, determined by case, motherboard and power supply. Power supplies convert from higher-voltage AC to lower-voltage DC and regulate the flow of electricity between the outlet and components which require differing voltages. Before working on a computer, Disconnect everything. Cables connect various components to power supply. Color-coded Connectors are keyed, meaning can be inserted only one way. Molex: 4-pin, rectangular 2 cut-off corners. Powers high-draw cooling fans, optical and hard drives. Berg: smaller 4-pin, powers floppy drives. Main connector: slotted, 2 rows of 20 or 24 pins, cables motherboard to power. Aux connector, also slotted but smaller, sometimes used for extra power. P8 and P9: Power connectors for older A.T. power supplies. Could be cabled backwards for disaster.


4 basic electrical units:

  • Volts V or E:force to push electrons through circuit.
  • Current, abreviated I: amount of electrons flowing through circuit. Current measured in Amps, A.
  • Power, P: measurement of current times voltage in circuit. Measured in Watts, abreviated W.
  • Resistance: R, Measures of opposition to current electrons encounter when flowing through circuit. Measured in Ohms. A good circuit's resistance is low.

Ohms Law

P -- Power I -- Current E -- electromotive force or volts) R -- resistance

P equals E I. Power equals Voltage times current. E Equals IR Voltage equals Current times resistance. Resistance equals voltage divided by current r = E/I If a power supply doesn't have a wattage rating you need to figure it out through current and voltage. Power supply must have capacity sufficient for all components; Power supplies are rated by wattage. Add up wattage required for all components to get minimum wattage that power supply should be rated for. Voltage selector switch on power supply must be set for your country. Set voltage too high and computer smokes; two low nothing works. auto ssensing power supplies are safest. Do not disassemble power supply, DANGER!

System Board

Buses are electrical pathways. Mother (system) board is main printed circuit board with CPU,ram and BIOS ROM chips, slots, heat sync, fan(s). Buses and connectors are also part of system board. A.T. form factor: old-fashioned foot-wide boards. ATX, smaller and improved with integrated case openings, 20-pin keyed power supply connector, and power can be toggled by sending a signal to the system board. Chipset: integrated circuits mounted on system board, enables data exchange between processor and components. Chipsets determine the type of connectors and supported amount of memory. Northbridge: RAM, video card and speed with which they communicate with CPU. Video is sometimes integrated in the northbridge; memory controller is sometimes integrated with the CPU. Minimizing interference Northbridge is located very close to the CPU. Southbridge: enables CPU to communicate with drives, usb and other i/O ports and sound.


CPu: processor, Does most calculations. pin-grid-array (PGA), 0-insertion-force. Its socket specification must match the chosen CPU. Processors can be single, dual, tripple or quad core. Refers to the number of them. Tripple is quad with one core disabled. Sockets -- determines type of CPU to install

Single core, Pentium 4

Socket 423 supports Pentium 4FC-PGA Socket 478 Supports Pentium 4/Celeron 4FCPGA-2 Socket T LGA775 supports Pentium/Celeron LGA755

Single Core AMD Sockets

Slot A supports Athlon SECC Socket A Supports Athlon, Athlon XP, Duron, Socket 754 supports Athlon 64

	Socket 939 supports Athlon 64 V.2

Socket 940 supports Athlon 64X Opteron

Server/WorkStation Sockets

Slot 2 (SC330) supports Pentium 2/3 Xeon Socket 603 supports Pentium Xeon (P4) Socket Pack418 supports Intel Itanium 2 Pac 611 Socket 940 supports AMD Athlon 64FX, Opteron

Pentium DualCores

Socket T (LGA775) Pentium XE, Intel Core 2 Duo, Intel Core 2 Extreme Socket M supports Pentium XE, Intel Core 2 Duo, Intel Core 2 Extreme

AMD 2 core processors

Socket S1 supports Athlon 64 X2, Turion 64 X2 Mobile Sempron, Turion 64 (MK series only) Socket AM2 (DDR2 but not DDR Memory) supports Athlon 64, Athlon 64 X2, Athlon 64 FX, Operton, Sampron, Phenom Socket AM2+ (Added support for DDR3) Socket 940 supports Athlon 64, Athlon 64 X2, Operton, Phenom series, Phenom X2Socket AM3 supports Phenom 2 (excluding 940 and 920), Athlon 2


Socket AM3 supports Phenom X3

Intel Quad Core

Socket LGA775 supports Intel Core2 Quad Socket F Supports these AMD processors: Operton 2xxx, 8xxx series, Athlon 64 FX FX-7x series, Phenom X4 series

Any Processor executes one instruction at a time. Cache memory stores remaining instructions and data for the running program.


RISC: reduced-instruction set. Fastest. Fewest number of instructions. Cisc: Complex Instruction set. Fewer steps for a single operation. PCS are CISC. Hyperthreading: multiple instructions executing simultaneously. Appears like multiple CPUS to the OS. MHZ: milions of cycles per second, measurement of CPU speed. Gigahertz GHZ: Billions of cycles. FSB: Front-side bus, 32-bit or 64 bits; wider is more powerful. Overclocking: running CPU faster than rated speed. Not recommended. Throttling: Slowing CPU to reduce heat and conserve power. MMX, replaced by SSE: instruction set for optimizing multimedia operations. Software must specifically use these instructions.


Components generate heat which is the enemy. Case fans and heat syncs keep temperatures down. There are also fans for cooling the gpu -- graphics processor unit.



ROM: Permanent Read-only memory, retains instructions when power is off. Cannot be ordinarily erased. Firmware is the software contained in ROM.

  • Ordinary rom programmed during manufacturer.
  • Prom is programmed after manufacture.
  • EPROM is erasable with UV light.
  • EEPROM is flashable.

Random Access (Writeable)

Ram: Temporary. erased when there's no power. Mor ram means better performance.

Dram (dynamic) needs constant refresh.

FPM memory is Dram mostly in old 486 PCS.

Sram (static) used for cache and doesn't need refresh.

SDRAM is synchronous dynamic ram, not to be confused with static RAM.

Single-channel memory: 64-bit transfer. Faster 128-bit transfers with dual-channel memory.

DDR: double-data-rate.Doubles maximum bandwidth; 2 transfers per cycle. DDR 2 and DDR3 even faster but not backward nor forward compatible. DDR 2 and 3 reduced noise and cross-talk between wires. DDR 2 and DDR 3 have a notch on the bottom.

EDO (extended data out) RAM, overlaps consecutive data access. CPU need not wait for one access to complete.

SDRAM: synchronis dynamic DRAM operating in concert with the memory bus.

RDRAM, so fast its use is uncommon.

Dynamic Ram Types

  • PC100 SDRAM transfers data at 800 MB/s and requires 100MHZ FSB
  • PC133 SDRAM transfers data at 1060MB/s and requires 133MHZ FSB
  • DDR-333 transfers data at 2700 MB/s and requires FSB running at 166MHZ
  • DDR-400 transfers data at 3200 MB/S and reqquires a FSB running at 200MHZ
  • DDR2-667 transfers data at 5333 NMB/s and requires a 667 MHZ FSB
  • DDR3-1600 transfers data at 12800 MB/S and requires FSB running at 1600 MHZ

Memory Modules

Circuit board holding RAM. Replaced old DIP chips which were soldered directly on the motherboard. Single inline memory Module (SIM) 30 and 72-pin configurations Dual inline memory modules: 168-pin SDRAM DIMMs, 184-pin DDR DIMMs, and 249-pin DDR2 DIMMs. RAMBus Inline Memory module: 184 pins RDRAM chips Small Outline DIM (SODIM): Reduced footprint for small spaces; 72-pins for 32-bit transfers; 144 pins for 64-bit transfers

   Modules can be single (ram on only one side) or double sided (RAM on both sides.)

L1 (level 1) cache is internal, L2 originally external, but now internal; L3 is external cache on high-end servers. Nonparity memory does no error checking. Parity memory: single-bit error checking with 1 extra parity bit ECC (error correcting code) memory: detects multiple-bit but can correct only single-bit errors

Slots and their adapter cards

The cards fit in slots to expand and customize the PC. Card connector must match slot type. Riser cards enabled horizontal fit in LPX slimline desktops.

  • ISA: older seldom used 8-bit or 16-bit "industry-standard architecture"
  • EISA (extended industry standard) 32-bit, also older
  • MCA (micro-channel architecture) IBM proprietary, 32-bit also old and seldom used.
  • AGP (advanced graphics port) 32-bit, older, for video cards
  • PCI (peripheral component interconnect): 32 or 64 bits, most computers use today
  • PCI-Express: x1, X4, x8 and X16 slots.

Cards include:

  • NIC and wireless NIC: Network interface cards.*
  • Sound and video adapters.
  • Capture Card: Sends video signal to computer for recording.
  • TV Tuner: connects PC to television source
  • Modem: connects PC to internet via phone line
  • Parallel and serial ports: connects to peripherals
  • SCSI (Small computer system interface): connects hard and tape drives

Floppy drives-- 3.5-inch magnetic discs720K or 1.44MB, usually A: and can boot PC. Internal Hard drive: storage in gigabytes, speed in revolutions per minute, usually C: SSD (solid state disk) internal with SATA or ATA interface, use flash chips, faster, need less power, no moving parts, same form factor as magnetic hard drives. Optical drives are CD (compact disc), DVD (digital versatile disk) or Blue-Ray disk (BD) and use lasers to read/write data.

Three optical media discs

  • CDS 700 MB
  • DVDS 4.3GB single-layer or or 8.5 GB on dual-layer.
  • BDS store 25GB on single-layer, 50GB on dual-layer.


  • CD-rom media: prerecorded.
  • CD-R record once.
  • CD-RW record multiple times.
  • DVD-Rom read-only.
  • DVD-RAM random access, record multiple times.
  • DVD+R or DVD-R: record only once.
  • DVD+RW and DVD-RW record multiple times
  • BD-ROM read-only-- games or video
  • BD-R record only once
  • BD-RI record multiple times

External storage can be flash (thumb) or removable magnetic drive. Internal drive connection interface must match motherboard controller.

Drive Interfaces

IDE (integrated drive electronics) uses 40-pin connector and is also called ATA (advanced technology attachment). ATA0-2 also uses 40-pin connector, is synonomous with EIDE (enhanced integrated drive electronics), supports over 512MB, uses DMA for speed and supports tape and optical drives on the controller's EIDE bus using ATAPI (attachment packet interface). 80 wires, 40 for grounding. PATA (Parallel ATA) drive controller interface. 40 pins, 80 wires, perhaps 40 wires on older PATA interfaces. SATA (Serial ATA) drive controller interface. 7 pin data connector. eSATA (external Serial ATA) drive controller interface. Hot-swappable with 7-pin data connector whose max length is 6.56 or 2 meters. SCSI (small computer system interface): both internal and external drives, up to 15 of them. Data connectors can have 50, 68 or 80 pins. RAID: redundant array of inexpensive disks-- seen as one logical drive Parity: detects errors Striping: write data across multiple drives. Mirroring: storing duplicate data to separate drives.

Raid Levels

  • 0: Striping, no mirroring, quick access, no backup.
  • 1: Mirroring, no striping. duplicates of each piece of data
  • 2: Unused.
  • 3: Byte-level striping, dedicated parity, slow, sequential requests best, no simultaneous read and write
  • 4: Block Striping with parity. Slow due to error checking, single drive is the bottleneck
  • 5: Striping: all drives used for parity, faster than 4. If one drive fails data can be rebuilt.
  • 6: Independent data disks with double parity. Slowest but can handle two drives failing.

Raid 0-1 combines both striping and mirroring for highest protection but also costs most for largest disks.


Case buttons and lights use front-panel cables to connect to motherboard. From power supply: Berg powers floppy drives, Molex powers PATA drives, SATA power cable for SATA drives. From drive controler, these data cables connect to respective drives. FDD ribbon floppy data cable, 34-pin ribbon from controler to drive, has a twist. Up to 2 34-pin connectors for floppy A and optional Floppy B. PATA, either IDE or EIDE: 40-pin cables. 2 connectors for drives, 1 for controller. PATA IDE: For transmission rates over 33.3 MBPS, cables with 80 wires and 40-pin connectors. 7-conductor SATA cable, one keyed connector for drive and another for controller. 7-conductor E-sata cable. SCSI data cables have colored stripe on pin 1; ensure you align it with pin 1 on drive and/or controller. Ensure you terminate SCSI chain. Cables resemble but carry different voltages from parallel. SCSI drive controller is called a host adapter.

Three types of SCSI data cables

  • Narow -- 50 conductors, up to 7 drives, 1 50-pin cable goes to host adapter.
  • Wide -- 68 conductors, up to 15 drives, 1 68-pin cable goes to host adapter.
  • Alt-4 -- 80 conductors, up to 15 drives, 1 80-pin connector to the host adapter.

Ports connect input/output peripherals

  • SCSI: Faster than 320 MBPS. For one device, max cable length is 80 feet or 24.4 meters. For multiple devices, max length is 40 feet or 12.2 meters.
  • Serial, RS-232:DB9 (DB25 is older) male, transmits 1 bit at a time, cable max length 50 feet or 15.2 meters.
  • Parallel, IEEE1284:25-pin DB25 female cabled to PC, 36-pin Centronics cabled to printer. 8 bits transmitted at a time. Max cable length 15 feet or 4.5 meters.
  • Modems: Use RJ-11 telephone cable.
  • Network, RJ45: Standard ethernet max 10MBPS, Fast ethernet 100 MBPS and gigabit Ethernet maxes out at 1000 MBPS. Max cable length 328 feet or 100M.
  • PS/2, 6-Pin female Mini-DIN: Green for mouse, purple for keyboard.
  • Audio: Line in, Line out, S/PDIF, Toslink, Game/midi, microphone.
  • USB, (Universal serial bus) 127 devices max, 480 MBPS max speed for USB 2.0.
  • Firewire, IEE1394 (I.Link): up to 63 devices. Standard allows some devices to power from the FireWire port. Max rate 400 MBPS, Max cable length 15 feet or 4.5 meters. Cables have 4 or 6 pins.

Video cable types

  • Component RGB: Red, green, blue, three RCA jack cables for analog video.
  • S-Video: 4-pin connector, analog video.
  • VGA (video graphics array), 3-row, 15-pin female connector, analogvideo
  • DVI (digital visual interface) 24 or 29 pin connectors, uncompressed digital video; dvi-i both analog and digital; dvi-d digital only.
  • HDMI (high-definition multimedia interface: 19-pin connector, digital video and digital audio output


Input devices: keyboard, mouse, touchscreen,microphone, cameras, scanners, biometric (fingerprint) sensors. KVM switch lets multiple PCS share Keyboard video and mouse. Output devices: monitor, speakers, printer.

3 monitor types:

  • CRT, (cathode-ray) big 3 electron beams
  • LCD: (liquid crystal) passive and active matrix also called TFT.
  • DLP (digital light processing) mostly for projectors, "all about the mirrors"
    Monitor resolution controls level of detail, higher resolution, better image quality.

Pixel (picture element) red, green or blue, a tiny dot. building block of the image. Dot pitch: distance between these dots. Contrast ratio, difference between intensity of brightest and darkest. Refresh rate: How often per second image is rebuilt. Higher rates reduce flicker, make better image. Interlace: first scans even then odd lines. Non Interlace: more modern monitors, scan from top to bottom. Vertical resolution: number of lines on screen Horizontal resolution: number of pixels in a line. Color Resolution: number of colors that monitor can produce. Aspect ratio: Horizontal to vertical measurement of the viewing area. Native resolution: Number of pixels a monitor has.

Monitor controls

  • Brightness: intensity
  • Contrast: Ratio of light to dark
  • Position: horizontal and vertical location of image
  • Reset: return to factory settings.

All-in-one printer: scan, copy, fax and print. Audio cards have amplifiers for headphone and speaker output. Different display standards, VGA, HDTV, WXSGA among others each have a native resolution and aspect ratio. Linear pixels: horizontal times vertical.

System Resources

IRQS: (interupt requests) components requesting information from CPU; its number determines its priority. Conflicts happen when two components share the same IRQ. Auto-assignment is done by plug and play. PCI allows for IRQ sharing between devices. Memorize table of IRQ numbers for A+.

I/O ports, 65535 of them; from 0000 thru FFFF hex. each component gets a unique address.

DMA: a channel that lets component communicate "directly" with memory bypassing CPU.

Lab Tips

1.1.2: Jobs. Search monster, Craigslist, companies in your local area. Doesn't have to be job you qualify for, but one you might enjoy performing. Should be related to computer technician work.

1.4.7: Researching components. Purchase from amazon, newegg, tigerdirect, CDW or similar. No need to set up account, log in or really buy. Study groups' audio available on cucat for walking through with past years' students.

--End of Module 1 Highlights.

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Page last modified on September 12, 2012, at 10:52 PM