CompTIA A+ 1101 - 3.5 Given a scenario, install, or replace the appropriate power supply

PSU

• computer uses DC voltage

• convert 120 V AC or 240 V AC to 3.3 V DC, 5 V DC, and 12 V DC

Ampere

• rate of electron flow past a point in one second

Voltage

• electrical “pressure” pushing the electrons

Power

• measured in watts (W)

• measurement of real power use

Alternating current (AC)

• direction of current constantly reverses

• distributes electricity efficiently over long distances

• frequency of this cycle is important

Direct current (DC)

• current moves in one direction with a constant voltage

+12V

• PCIe adapters, hard drive motors, cooling fans, most modern components

+5V

• some motherboard components

+3.3V

• M.2 slots, RAM slots, motherboard logic circuits

+5VSB

• standby voltage

-12V

• integrated LAN

• older serial ports

• some PCI cards

-5V

• available for ISA adapter cards

• most cards didn’t use it

• today’s motherboards don’t have ISA slots

24-pin motherboard power

• main motherboard power

• provides +3.3V, ±5V, and ±12V

20-pin motherboard power

• original ATX standard

• 24-pin was added for PCIe power

Redundant power supply

• two (or more) power supplies

• internal to the server

• each power supply can handle 100% of the load

• hot-swappable

Fixed connectors

• connected to the power supply

• may have too many connectors

• may not have enough

Modular power supply

• add cables as needed

• fewer leftover wires, better airflow

• a bit more expensive

Wattage rating

• indicates the maximum amount of electrical power that a device can safely handle