• Wattage rating
• PSU fan not turning
• Case fans
Missing slot covers (front and back
Thursday, 4 August 2011
PSU Ratings
• Watts (w)
• 250 – 400W
• More devices requires more watts
• More powerful PSUs generate more heat
Molex Connector
• 4 pins/wires
• Supplies 12V, 5V and ground to devices
• Hard drive, CD/DVD, ZIP
• Chamfers
Power Terms - Summary
• Pressure = Voltage (V)
• Volume Flowing = Amperes (A)
• Work = Wattage (W)
• Resistance = Ohms (Ω)
• Fuses and Ground Wires
• An electrical outlet must have a ground wire to be suitable for PC use
Power Terms
• Joules (J) = Energy
• Volts (V) = Voltage (pressure of electrons in the wire)
• Amps (A) = Current (amount of electrons moving past a certain point in the wire)
• Watts (W) = Measure of power (how many amps and volts a device needs to work)
• Ohms (Ω) = resistance (how much the wire resists the flow of electrons)
Power Terms
• Joules (J) = Energy
• Volts (V) = Voltage (pressure of electrons in the wire)
• Amps (A) = Current (amount of electrons moving past a certain point in the wire)
• Watts (W) = Measure of power (how many amps and volts a device needs to work)
• Ohms (Ω) = resistance (how much the wire resists the flow of electrons)
UPS
• Uninterruptable Power Supply
• Protects PC from brownouts and blackouts
• Two types: Online (UPS) and Standby (SPS)
• Most UPSs include surge suppressors
• Essentially a sophisticated and big battery
• Rated in Watts
• NB. Never connect a printer to a UPS
Surge Suppressors
• Protects PC from voltage spikes
• Between PC and wall socket
• At least 800-1000 Joule(J) rating
• Joule = a measure of energy
• A higher joule rating means you can be protected from a more powerful power surge
Preventing ESD
• Design Tech Support Room well
• Discharge static build-up
• Anti-static strap
• Anti-static mat
• Don’t place components on metal surfaces
• Anti-static bags
ESD
• Electrostatic Discharge
• Transfers through human body and metals
• 30V of static can destroy a chip
• Examples of Static
• Walking on carpet = 1500 – 25000V
• Picking up a plastic bag = 1200 – 20000V
ATX 12v Connector
• Provided by most modern PSUs
• 4 pin notched connector
• Gives an extra 12v to the motherboard
• Athlon XP/Pentium 4 motherboards
External Connection
• 3 pin male “IEC-320 connector”
• 3 pin female “IEC-320-2-2” connector on older models.
ATX Power Connectors
• Single P1 instead of P8 and P9
• 20 pin notched connector
ATX PSU Connectors
• Molex Hard drive, CD/DVD drive, Zip drive
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• Mini FDD
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• Sub-mini Fans
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• Splitter Adaptor that allows 2 devices to share the same
• molex connector
• Serial ATA Hard drive
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ATX Power Switch
• “Soft Power”
• Constantly supplies 5V to the PC
• Never off
• Separate on/off switch
PSU - ATX
• Replaced the AT PSU
• Used with ATX case and motherboard
• P1 power connector
• Supplies +3.3V / +2.8V to motherboard
• Can’t use an AT PSU with an ATX motherboard and vice versa
PSU - AT
• P8 + P9
• Black to Black with the black wires in the centre
• AT power switch
• Doesn’t support hibernate mode
• Wake on modem/LAN not supported
Power Supplies
Function of the PSU
• Converts 230V AC to +5V –5V and +12V – 12V DC
• 3 main functions
• Steps down voltage
• Changes from AC to DC
• Smoothes out power sags and spikes
• Also helps to cool the PC components
Accessing BIOS through CMOS setup
• CMOS can only be accessed when the PC is booting
• Key combination at start-up
• Changes are stored on a NVRAM CMOS chip
• AMI and AWARD BIOS – DEL key
• PHOENIX BIOS – CTRL, ALT and ESC keys or F2
• The mouse doesn’t work in CMOS setup!
CMOS
• Complementary Metal Oxide Semi-Conductor
• Stores roughly 64Kb of data
• Part of the Southbridge in most PCs
• Specs stored in CMOS must match hardware
• Allows you to access the BIOS
• When hardware is changed/updated, CMOS must be updated
Updating the BIOS
• Original BIOS chips couldn’t be updated
• EEPROM or Flash ROM
• Why update?
• Support for new hardware
• Overcome a BIOS bug
• “Flashing” the BIOS
• BIOS updates downloaded from Internet
BIOS TYPES
• Motherboard chipsets
• Each BIOS designed for a specific chipset
• 2Mb of storage
• 8088 PC – 384K
• Backward compatability
• BIOS Manufacturers
• AMI
• Award
Phoenix
BOOT Process in detail
• CPU’s power good wire “wakes up” the CPU
• CPU reads first line of POST program
• Bootstrap loader runs
• Check if disk is in FDD drive
• Look for O.S. on boot sector of hard drive
• NTLDR (Windows 2000/XP) or IO.SYS is loaded into RAM
• Control is transferred from bootstrap loader to the O.S.
• Core O.S. files, drivers and services are loaded into RAM
A detailed look at POST
• “Devices go forth and test yourselves”
• Only checks devices listed in BIOS
• Beep codes
• Refer to motherboard manual
• Text errors
• “Missing NTLDR”
• “Keyboard error or no keyboard present”
• POST cards
Startup Routine
• 1. During the POST, the BIOS tells drivers to “test themselves” and report back
• Problems are flagged either by beeps codes or by messages on the screen
• e.g. 301 Keyboard failure
• 2. Bootstrap Loader
• 3. Master Boot Record
• IO.SYS
• NTLDR
• After this the operating system takes over
Function of the BIOS
• Stores a set of instructions to tell the PC how to control devices
• Provides low-level hardware access
• Tests hardware on startup using POST
• Runs “bootstrap loader” after POST
• After this the operating system takes over
BIOS
• Basic Input Output System
• A chip on the motherboard
• BIOS is stored in the PC’s ROM chip
• EPROM
• Firmware
• BIOS will support all hardware on an 286 AT PC
• Drivers are required for all other hardware
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