// HARDWARE MODULE 06

Power Supply Unit Facts & Specifications

CYBERGRIND.ORG
HW-006
v1.0 // 2026
PSU Overview
The Power Supply Unit (PSU) converts alternating current (AC) from the wall outlet into the low-voltage direct current (DC) required by all internal components. Modern personal computers universally use switched-mode power supplies conforming to the ATX standard.
AC to DC Conversion Flow
AC Mains (120/240V)→
Rectifier→
Transformer→
Regulator→
DC Rails (3.3V / 5V / 12V)
Voltage Rails
RailPowers
+12VCPU, GPU, motors (fans, HDDs) — highest current demand
+5VUSB ports, older drives, some logic circuits
+3.3VRAM, PCIe slots, modern logic circuits
+5VSBStandby power — always on while PSU is connected to AC
Wattage Requirements

Standard Desktop

300W – 500W. No discrete GPU or high-end CPU. Office PCs, basic workstations, media servers.

Gaming / High-Performance

650W – 1000W+. Discrete GPU + high-TDP CPU. RTX 4090 / RX 7900 XTX setups may need 850W+.

Quality matters as much as wattage. A high-quality 650W PSU is safer than a low-quality 850W unit with poor voltage regulation. Look for 80 PLUS certification (Bronze, Gold, Platinum, Titanium).
ATX Key Behaviors

5VSB Always On

While plugged into AC power, the PSU always provides 5-Volt Standby power for wake-on-LAN and USB charging.

PS_ON Signal

The PSU turns on and off via a signal from the motherboard — not directly from the power button.

Power Good Signal

PSU sends a "power good" signal when DC voltages are within spec — the CPU only begins execution after receiving this.

Failure Symptoms
⚠ PSU Failure Indicators
Random restarts with no BSOD, system freezes under load, failure to POST, USB devices losing power intermittently, burning smell or audible coil whine. PSU failures are often misdiagnosed as RAM or CPU issues — always isolate the PSU first.
CYBERGRIND.ORG // HARDWARE SERIES // HW-006 SOURCES: Wikipedia.org · EcoFlow.com © 2026 CYBERGRIND