Installing a Desktop Power Supply — Core Points

Role of the Power Supply

• Converts wall AC (US $120$ V or EU $230$ V) to DC rails: $3.3$ V, $5$ V, $12$ V
• Provides sufficient wattage (e.g.
  • Gaming/​high-end build: $750{-}850$ W
  • Office/​basic build: lower wattage acceptable)

Modular vs. Non-Modular Units

• Modular (detachable) cables: better airflow, only plug needed leads
• Non-modular (fixed) cables: common in standard office desktops

Common PSU Connectors

• 24-pin ATX (mainboard power)
  • Older boards: $20$-pin or $20{+}4$ option
• 8-pin EPS/CPU power
• PCIe 6{+}2-pin (graphics cards; supports $6$- or $8$-pin)
• SATA $15$-pin (SSD/HDD/optical)
• Molex $4$-pin (legacy peripherals)

Physical Installation

• Fan faces downwards (if bottom-vented case) to exhaust heat out of chassis
• Slide PSU in from motherboard side if rear lip blocks direct insertion
• Secure with four screws at rear mounting points; re-tighten for stability

Cable Routing

• Feed cables through rear/bottom grommet before motherboard area for cleaner build
• Essential initial connections:
  • 24-pin ATX ⇒ motherboard edge
  • 8-pin CPU ⇒ top-rear motherboard socket
• Leave SATA & PCIe leads aside until drives/GPU are installed

Voltage Selection & Safety

• Modern units: auto-sensing $120/230$ V—no switch required
• Older PSUs: manual switch (use $110/120$ V in US; $220/240$ V in EU/Asia) to avoid damage

Quick Checklist

• Confirm wattage headroom for GPU & CPU
• Attach correct connectors; ensure latch clicks
• Keep unused modular leads out to maximize airflow
• Verify PSU fan type (quiet mode may delay spin until load/heat increases)
• Double-check voltage setting before first power-on