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Difficulty: MediumExpansion Cards and Power Supplies

A system administrator is upgrading a desktop workstation by installing a dedicated PCI Express graphics card rated at 250 W250\text{ W} TDP. The existing system components (CPU, motherboard, RAM, and storage) draw a combined total of 165 W165\text{ W} under peak load. To maintain hardware longevity and efficiency, the workstation's total continuous power draw must not exceed 80%80\% of the power supply unit's (PSU) total rated capacity. Which of the following represents the minimum standard PSU wattage rating required for this upgraded system?

  1. A
    415 W415\text{ W}
  2. B
    500 W500\text{ W}
  3. 550 W550\text{ W}Answer
  4. D
    650 W650\text{ W}

Answer

A 550 W550\text{ W} power supply unit is the minimum standard rating required.
Total continuous power draw is calculated by adding the GPU power (250 W250\text{ W}) to the rest of the workstation components (165 W165\text{ W}), resulting in 415 W415\text{ W}. To meet the requirement that 415 W415\text{ W} does not exceed 80%80\% of total rating, calculate 4150.80=518.75 W\frac{415}{0.80} = 518.75\text{ W}. The smallest standard PSU rating that meets or exceeds 518.75 W518.75\text{ W} is 550 W550\text{ W}.

Step-by-Step Solution

1
Calculate total peak component power draw
250 W+165 W=415 W250\text{ W} + 165\text{ W} = 415\text{ W} continuous load
Summing GPU power consumption with the combined draw of all other system hardware gives total system demand.
2
Apply the 80% maximum workload constraint to find minimum required PSU wattage
415 W0.80=518.75 W\frac{415\text{ W}}{0.80} = 518.75\text{ W}
To ensure peak system load does not exceed 80% of PSU capacity, total draw is divided by 0.80.
3
Select the next highest standard PSU capacity rating
A 550 W550\text{ W} power supply unit
Because power supplies are sold in discrete capacity increments, the minimum standard rating exceeding 518.75 W518.75\text{ W} is 550 W550\text{ W}.

Key Concept

Power supply sizing calculations and recommended continuous load overhead margins
Estimated Time:1m 30s
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Topics

Expansion Cards and Power Supplies

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