The Power Supply
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As all active components in a computer are electrical devices,
they must be supplied with power. The power supply takes 220 Volts
Alternating Current (AC) as input and supplies both 12 Volts
Direct Current (DC) for disks and fans, and 5 Volts DC for the
motherboard and expansion cards.
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A 230 W Power supply (transparent for educational
purposes only)
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Power supplies are standardized in size to fit all system units.
They differ in performance, however: a normal power supply for PCs has
90 to 150 W, but there are also stronger ones with 200 W,
250 W, and 300 W, respectively.
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The biggest power consumers are RAM and
CPU. The graphics adaptor's RAM counts as well!
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Thumb rules for deciding the minimum performance:
- For an office PC 90 W is enaugh.
- + 30 W for AMD CPUs
- + 30 W for every full 256 MB main memory
- + 30 W for every full 32 MB RAM on the graphic adaptor
- + 30 W if there are more than 3 expansion cards in the PC
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