Review Index:

SilverStone Zeus ST85ZF 850W Power Supply Review

Manufacturer: Silverstone

Introduction and Features

SilverStone Technology, Inc. recently added a new 850W power supply to their Zeus high output line.  The ST85ZF is very similar to the Zeus 750W power supply but the 850W now includes four hard-wired 6-pin PCI-e connectors in addition to an extra 100 watts of output capacity. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />



SilverStone is based in <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Taiwan with a sales office in California.  They specialize in designing low acoustic and high performance PC and HTPC enclosures, power supplies and other accessories for the PC enthusiast market. 


SilverStone Zeus ST85ZF 850W PSU Key Features:


  • 850 watt continuous power output

  • ATX12V v2.2 and EPS12V support

  • Quad +12V outputs (up to 70A combined +12V)

  • Quad PCI-e 6-pin connectors

  • Industrial grade components

  • Efficiency greater than 80%

  • Active PFC with Universal AC line input

  • 3-Year warranty 

In addition to the power supply the box also includes a heavy duty power cord, mounting screws, wire ties, 8-pin to 4-pin +12V ATX adapter, and printed manual.  If you are interested in seeing what really makes this power supply tick, a very detailed, 13-page electrical specifications document is available on the SilverStone website.



The Zeus 850W power supply was evaluated on both features and performance.  A full range of equipment was used to test the power supply under controlled load conditions.  In addition to measuring the power going in and coming out I looked at voltage regulation, electrical noise (AC ripple), sound level, efficiency and cost.  Here is a list of the equipment used during testing.



  • FLUKE 87-III True RMS digital multimeter (Accuracy ±0.05%)

  • Extech 380803 Power Analyzer (Accuracy ±0.5% of full scale)

  • Hitachi V-650F 60 MHz dual trace oscilloscope (Accuracy ±3%)

  • Powerstat Variable Autotransformer, 1.4 KVA, 0-140 VAC

  • FLUKE  52-II digital thermometer (Accuracy ±0.3ºC/0.5ºF)

  • Extech Model 407736 digital sound level meter (Accuracy ±1.5 dB)

  • AccuLab V1-10kg digital balance (Accuracy ±1g)

  • Homemade PSU load tester — selectable loads (up to 470W)

  • (2) CSI3710A Programmable DC load (up to 150W each)

  • (2) CSI3711A Programmable DC load (up to 300W each)

Establishing a controlled load is critical to testing and evaluating a PC power supply.  In addition to my own home-made load tester, I'm now using four programmable DC loads for greater flexibility and accuracy.  This new combination can place up 1,400 watt load on the unit being tested. 



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