3.5 Power Supplies Flashcards
Given a scenario, install or replace the appropriate power supply
A computer enthusiast is completely modifying the inner workings of a computer, even down to the electrical level. The enthusiast has an ATX power supply unit and is looking at the wiring. Which of the following are accurate assessments? (Select all that apply.)
-Black wires are Ground
-Yellow wire are 12V
-Orange wires are 5V
-Red wires are 3.3V
Black wires are ground & yellow wires are 12V
*Wires with black insulation are ground. The advanced technology extended power supply unit (ATX PSU) standard has gone through several revisions, specifying different connector form factors. In the original ATX specification, the P1 connector is 20-pin (2x10).
*Yellow wires are +12V. A computer system may be fitted with two PSUs, one acting as a failover redundant power supply. If modifying the rig, then the enthusiast should add a second PSU.
~Orange wires are +3.3V. The power connectors supply DC voltage to the motherboard and devices at 3.3 VDC, 5 VDC, and 12 VDC.
~Red wires are +5V. Not all components use power at precisely these voltages.
An employee’s computer is damaged, so they took it to the company help desk. The technician found that damage occurred to the power component. Which of the following most likely happened?
-The user plugged a 240V adapter into a 120V
-The user plugged a 5V adapter into a 12V supply
-The user plugged a 120 V adapter into a240V supply
-The user plugged a 12V adapter into a 5V supply
The user plugged a 120V adapter into a 240V supply
~Plugging a fixed-input 110–120V adapter into a 220–240V power supply will likely cause damage.
~Plugging a fixed-input 220–240V adapter into a 110–120V supply will not cause any damage, although the laptop will not work.
~The power supply unit (PSU) supplies 12V power immediately, and the fans and hard disks should spin up.
~After the PSU boots up, it tests its 5V and 3.3V supplies. When it is sure that it provides a stable supply, the PSU sends a power-good signal to the processor.
A retired penetration tester devotes time to helping and teaching people. The pen tester acquires older technology to help with teaching, and as the years go by, the pen tester swaps components to keep costs low. Unfortunately, some of the power supply units (PSUs) are starting to die out, and the tester finds that the newer units do not connect properly with the motherboard. What is the best option to buy for compatibility?
-20+4 pin P1 adapter cable
-2x12 P1 form factor
-Modular PSU
-Redundant PDU
20+4 pin P1 adapater cable
~Some power supply units (PSUs) have a 20+4-pin P1 adapter cable for compatibility with older motherboards with a 20-pin port.
~Most systems follow the ATX12V version 2 specification, which defines a 24-pin (2x12) P1 form factor to replace the 20-pin one.
~A modular PSU has power connector cables that are detachable from the unit. Reducing the number of cables to the minimum required minimizes clutter within the chassis.
~A technician may fit a computer system with two PSUs, one acting as a failover redundant power supply that could also connect to a different grid power circuit.
A computer repair specialist diagnoses an issue with a peripheral component interconnect (PCI) card for a user. The user has a much older computer but is replacing parts to improve the overall computer operations without paying the cost of a brand new computer. However, the specialist notices that the keying does not quite line up. What is the reason it is not working?
-A 3.3V card was inserted in a 5V slot
-A 5V card was inserted into a 12V slot
-The user plugged a 120V adapter into a 240V supply
-A 5V card was inserted in a 3,3V slot
A 3.3V card was inserted in a 5V slot
*To prevent a user from inserting an incompatible PCI card into a motherboard slot (for example, a 3.3V card in a 5V PCI slot), the keying for the three types of cards is different.
~The earliest PCI cards were for 5V signaling. More recently, 3.3V and dual voltage PCI cards became more prevalent.
~The power supply unit (PSU) supplies 12V power immediately, and the fans and hard disks should spin up. PCI cards are 5V and 3.3V.
~Power adapters for computers come in 110-120V and 220-240V. PCI cards come in 5V and 3.3V.
A recent U.S. high school graduate is attending a university overseas in Europe. The graduate has a desktop and swaps out the power supply unit (PSU) to match European standards. What does the high school graduate swap out the PSU for?
-12V
-220V
-120V
-5V
220V
*In Europe, the voltage is 220-240 VAC (high-line). AC voltage supply varies by country and by the nature of AC distribution circuits. Consequently, PSUs have quite a wide tolerance in each band.
~A 120V power supply unit (PSU) is only for North America, where the input voltage for most homes and offices is 120 VAC (low-line).
~A 12V rail is used off the PSU to internal components. For a modern computer, the output rating of the +12 VDC rail (or rails) is the most important factor and the most heavily used.
~A power supply unit (PSU) provides 12V, 5V, and 3.3V rails.
A user’s machine recently traveled abroad, and the computer will not start up properly after returning from the trip. Which of the following is the most likely cause?
-The user plugged a 5V adapter into a 12V supply
-The user plugged a 12V adapter into a 5V supply
-The user plugged a 120V adapter into a 240V supply
-The user plugged a 240V adapter into a 120V supply
The user plugged a 120V adapter into a 240V supply
*Plugging a fixed-input 110–120V adapter into a 220–240V power supply will likely cause damage.
~Plugging a fixed-input 220–240V adapter into a 110–120V supply will not cause any damage, although the laptop will not work.
~The power supply unit (PSU) supplies 12V power immediately, and the fans and hard disks should spin up.
~After the PSU boots up, it tests its 5V and 3.3V supplies. When it is sure that it provides a stable supply, the PSU sends a power-good signal to the processor.
A computer engineer is designing a custom new gaming laptop and is currently designing power output and connections. Which rail is the most important to consider?
-12V
-5V
-120V
-3.3V
12V
*For a modern computer, the output rating of the +12 VDC rail (or rails) is the most important factor and the most heavily used.
~The output of 5V has a combined limit. A rail is a wire providing current at a particular voltage.
~Note that the output of +3.3V also has a combined limit. Distribution refers to how much power gets supplied over each rail.
~A power supply unit (PSU) provides rails of 12V, 5V, and 3.3V. A PSU of 120V is only for use in North America.
An avid technical enthusiast recently purchased a newly upgraded ENERGY STAR 80 PLUS mining rig, which operates on a 500W supply. The technical enthusiast wants to calculate the cost of power consumption, compare it to the value of bitcoin mined, and see how long it takes to break even. How much power should the enthusiast estimate the mining rig to use?
-200-300W
-500W
-400W
-625W
625W= 500W divided by .8 (80%)
An ENERGY STAR 80 PLUS compliant power supply unit (PSU) must be 80% efficient at 20–100% of the load. Dividing 0.80 into 500W would give an expected output of 625W.
~500W is the amount of power required, but much of the energy is lost mainly as heat. Therefore, as energy becomes more expensive, power efficiency becomes an important criterion when selecting a PSU.
~400W would be an incorrect calculation. Where 0.80 divides into 500W to find the expected output needed, 400W would be the wattage when multiplying 500 by 0.80.
~A standard desktop typically rates at around 200–300W. However, a mining rig is not a standard desktop.
A graphic artist bought the latest and greatest graphics card for a desktop but heard it runs hot. The artist wants to remove any unnecessary cabling inside the desktop, to get the best possible air circulation to cool the graphics card during peak operations. What should the artist use?
-Modular PSU
-SSD
-Redundant PSU
-EIDE
Modular PSU
*A modular power supply unit (PSU) has power connector cables that are detachable from the unit. Reducing the number of cables to the minimum required minimizes clutter within the chassis, improving airflow and cooling.
~A redundant PSU would run hotter. The configuration also requires a compatible motherboard.
~A solid-state drive (SSD) uses flash memory technology to implement persistent mass storage. Flash memory performs much better than the mechanical components.
~An enhanced integrated drive electronics (EIDE) cable typically has three color-coded connectors. The blue connector is for the motherboard port. The black (end) and grey (middle) connectors attach to devices 0 and 1, respectively.
A curious IT student is looking at a piece of hardware in class with redundant power supplies. What type of hardware is the student most likely looking at?
-Desktop
-Laptop
-Server
-Cell phone
Server
*Redundant power supply configurations are more common on server systems than on desktop PCs. Typically, each power supply unit (PSU) plugs into a backplane on a server and is hot-swappable.
~While it is possible to have multiple power supply units (PSUs) in a desktop, a redundant PSU configuration requires a compatible motherboard.
~A laptop has a small form factor and typically does not support having a second PSU. However, a technician may fit a computer system with two PSUs, one acting as a failover redundant power supply.
~Cell phones do not typically have a second PSU, although many people do carry around a second battery.
An avid gamer is building a gaming desktop from the ground up and is calculating power requirements and looking at power supply units (PSUs) that will handle the power spikes. What is the measurement for the PSU’s output capability?
-Voltage rating
-Alternate or direct
-Wattage rating
-Current rating
Wattage rating= voltage multiplied by current (V*I)
*The wattage rating is the power supply unit’s (PSU’s) output capability measurement. For example, a PSU designed for use in a standard desktop PC typically rates at around 200–300W.
~Voltage is one component used to calculate wattage. Power is measured in watts (W), calculated for electrical components as voltage multiplied by current (V*I).
~Current is the other component used to calculate wattage. When working with power, the current is the primary safety concern because too much current is the part of electricity that can kill someone.
~A PSU contains a rectifier to convert alternating current (AC) to direct current (DC), transformers to step down to lower voltages, and filters to ensure consistent output voltage levels.
