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Power supply and redundancy in the PC

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Power supply and redundancy in the PC

In short: The power supply converts mains voltage (230 V alternating current) into low direct voltages for all components. Redundancy means keeping important parts in duplicate so that the failure of one part does not stop operation.

In more detail: The power supply unit (PSU) delivers +12 V, +5 V, +3.3 V and a standby voltage. On the motherboard, voltage regulators (VRM) make the exact small voltages for CPU and RAM from them. Important systems have several power supplies and several circuits.

In Depth

Paths of current in the PC:

  1. Wall socket (230 V AC) → power supply.
  2. Power supply: rectify, switch, convert → +12 V, +5 V, +3.3 V DC.
  3. 24-pin ATX connector (motherboard), 8-pin CPU connector (EPS), PCIe connector (graphics card), SATA connector (drives).
  4. VRM on the motherboard → 1.0 – 1.4 V for the CPU.
  5. Power-good signal reports stable values.

Important characteristics of a power supply:

  • Power (watts): Must fit the hardware, with reserve. 550 – 750 W are enough for a gaming PC.
  • Efficiency (80 PLUS Bronze/Gold/Platinum): Share that really arrives, the rest becomes heat.
  • Protection circuits: OVP/UVP (over/under voltage), OCP (overcurrent), SCP (short circuit), OTP (over temperature).
  • Modular: Cables can be detached, tidier build.

Redundancy in the power supply:

  • Redundant power supplies (N+1, 1+1, 2N): Two or more supplies share the load. If one fails, the other takes over. Servers have them hot-swappable (replaceable during operation).
  • Two independent circuits: Each supply hangs on its own circuit (A and B side in the data center).
  • UPS (uninterruptible power supply): A battery bridges power outages and lets the computer shut down in an orderly way.
  • Emergency generator secures longer outages in data centers.

Why redundancy? A single point of failure would otherwise bring everything down. Costs rise, and so does availability. Example: 99.9 % availability means nearly 9 hours of downtime a year, 99.99 % only 52 minutes.

Redundancy elsewhere: RAID for disks, double network cards, clusters, two data centers. Redundancy does not replace backups.

See also: Redundancy, Power supply (PSU) and 80 PLUS, Power-good signal

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