International Journal of Power System Operation and Energy Management

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Knowing the actual power requirement of each individual component in a desktop computer is useful when sizing a power supply or when upgrading the PC. In this paper the power demand by various components within six different computer systems was investigated. Measurements of the actual current drawn from each voltage rail when idle and when in use were made and the data examined. The results obtained showed that the total power drawn at idle and on CPU load test was mainly due to the load demand on the +12V rails and this varied significantly between the computer systems; meanwhile +5V and +3.3V lines drew very little power and the total power consumed did not vary significantly between systems on idle state. The assessment revealed that it is highly unlikely that a modern computer system will ever overload either the +5V or +3.3V rails of an ATX12V 2.x compliant power supply; the +12 rails on the other hand, are very heavily used especially under load. Thus, it is very likely that the ratings for the +12V rails is more important than the total wattage rating when it comes choosing a power supply unit for a computer system.