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Black rectangular ATX power supply with 140mm fan grille and modular cable ports

Lian Li

Lian Li SX1200P.B 1200 W ATX 3.1 PCIe 5.1 Platinum power supply

SKU CH-NWG0-T3PAJ MPN SX1200P.B

Delivers 1200 W through ATX 3.1 and PCIe 5.1 with 80 Plus Platinum efficiency, 100 % Japanese 105 °C capacitors, a 12V-2x6 connector.

  • Max wattage1200 W
  • Power factor correctionActive PFC, PF > 0.95 under full load @ 115Vac, 60 Hz
  • PSU noise rating39.9 dB
  • AC input frequency100-240Vac
  • Mean time between failures100,000 hrs minimum 25℃/75% Load
  • Product typeATX

Model 1200W Black

  • 80 Plus Platinum efficiency delivers up to 94% conversion at 50% load
  • Fanless operation up to 40% load for silent low-load performance
  • ATX 3.1 and PCIe 5.1 compliant with 12V-2x6 high-current connector
  • Fully modular braided cables with combs simplify cable management and airflow
  • 100% Japanese 105°C capacitors and 100,000-hour MTBF ensure long-term reliability

Platinum 1200 W ATX 3.1 power supply

This 1200 watt ATX power supply meets ATX 3.1 and PCIe 5.1 specifications and carries 80 Plus Platinum certification. It is built for high-end desktop systems that demand stable +12 V delivery and high efficiency. The fully modular design suits builders who want to install only the cables their configuration requires.

ATX 3.1 and PCIe 5.1 practical limits

The unit complies with ATX 3.1 and PCIe 5.1, so it supports the 12V-2x6 connector for modern graphics cards. Efficiency reaches up to 94 percent at 50 percent load, and active PFC maintains a power factor above 0.95 at 115 Vac input. The fanless smart stop operates at or below 40 percent load, reducing noise when the system is idle or under light demand.

Build quality and daily use

All capacitors are Japanese 105 degree C rated for long-term reliability, and the 12V-2x6 terminals use high-current copper alloy. Braided cables with included combs simplify routing in compact cases measuring 150 mm wide, 86 mm high and 140 mm deep. A rear switch lets the user enable or disable the fanless mode, while the 140 mm fan runs at 39.9 dB when active.

How it compares

Measured against everything we stock in ATX Desktop Power Supplies, at today’s prices. Recalculated every night.

Price $119.99
Cheaper than about 59% of the 10,869 comparable items (median $142.99).
Max wattage 1200 W
Higher than about 90% of the 930 comparable items (median 850 W).

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Specifications

Product
Brand nameLIAN LI
Product typeATX
Power
Max wattage1200 W
Power factor correctionActive PFC, PF > 0.95 under full load @ 115Vac, 60 Hz
AC input frequency100-240Vac
Size & build
Product dimensions150 mm(W)x86 mm(H)x140 mm(D)
Shipping weight3.27 kg
Package size152 × 140 × 89 mm
Environment & compliance
PSU noise rating39.9 dB
More details
Mean time between failures100,000 hrs minimum 25℃/75% Load

Other versions of this model

3 more in the same range

Questions about this item

Should I pick the 1200 W model or a lower-wattage unit?

Choose the 1200 W version if your build draws near that level under full load; it delivers up to 94% efficiency at 50% load and meets 80 PLUS Platinum targets, while the fan stays off until 40% load for quiet idle operation.

What does the 1200 W rating mean once the PSU is installed?

It can supply a continuous 1200 W to your components with active PFC above 0.95 at 115 V, 60 Hz, and the 140 mm fan keeps noise around 39.9 dB even at higher loads.

How do the ATX 3.1 and PCIe 5.1 labels affect what I can plug in?

The unit includes a native 12V-2x6 cable rated for the PCIe 5.1 power spec, so current-generation graphics cards connect directly without adapters, and the ATX 3.1 design supports modern power-excursion requirements.

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