Zalman 850W Heatpipe Cooled PSU - 650W Load Test and Final Thoughts

Article Index
Zalman 850W Heatpipe Cooled PSU
ZM850-HP Features and Specs
ZM850-HP Cables and Inside
Test Setup, Methods and Testing
650W Load Test and Final Thoughts

650W Load Tests:

We've seen the Zalman PSU start off quite well with non-load and 200W load values, but things start to weaken as we run higher loads through this PSU.  It is rated for 850W, and while we can't run this at 100% load, we can still push it with a pretty powerful system in real world tests.  We record the results with a Tektronix TDS2002 scope, and this is how it shapes up under some pretty heavy testing.

 3.3v at 650W
3.3v at 650W
 5v at 650W
5v at 650W

 

Under a fairly heavy load the 3.3v line and the +5v line remain in the low 40mV range and are under the 50mV requirement - but not by a whole lot.  If this curve were to continue, we'd see results out of spec at 850W - if we could load up the PSU that heavily.  The reality is that many people who would draw 800W+ are going to buy a bigger PSU, but if it's rated at 850W, it should be able to perform within spec at the rated load.

As we jump into the 12v rails, we'll cover what each rail does as we go.

 12v1 at 650W
12v1 at 650W
12v2 at 650W
12v2 at 650W

 

As you can see above, things are getting more interesting. . . The +12v1 rail is the main motherboard 24 pin connector and is responsible for many of the system functions.  This rail is reporting at 86mV peak-to-peak values, and while it is within spec, it is still pretty whacky.  The +12v2 rail is used for the 4/8 pin CPU connector and is also showing signs of stress.  It is a bit lower at 78mV, but it is still quite noisy and shows a noticeable ripple.

+12v3 and +12v4 are for PCIe connectors 1 and 2 and are connected to separate 8800GTX graphics cards.  The results below have been taken during 3DMark06 at 2560x1600 with 8x AA and 16x AF.  These cards are overclocked and working pretty hard as you can see below.

 12v3 at 650W
12v3 at 650W
12v4 at 650W
12v4 at 650W

 

These rails are also showing signs of stress and have a much higher ripple and noise reading that the Thermaltake Toughpower with its heftier 12v rails.  The +12v3 rail is averaging 64mV peak-to-peak while the +12v4 rails measures 76mV peak-to-peak.

The +12v5 rail s shared between PCIe 3 and the ODD/HDD Molex connectors.  Remember there are a total of 10 ODD/HDD connectors as well as 2 Floppy connectors, so sharing this 18A rail with a graphics card is pretty risky.  If the rail had higher amperage, it would help, but if you had all twelve connectors used, as well as a graphics cards, you'd be in bad shape.

 12v5 at 650W
12v5 at 650W
12v6 at 650W
12v6 at 650W

 

The +12v6 rail is shared between the fourth PCIe connector as well as with the 12 SATA connectors.  My concerns are the same as with the shared Molex/PCIe connector, and the results above speak for themselves.  Overall, ripple and noise remained within spec, but the 12v5 rail was up to 70mV while the 12v6 line held at 64mV.  Not a very impressive showing, but within specification all around.

Below are the charts that show average voltage as well as average peak-to-peak ripple and noise.

Ave. Voltage

 

 Ave. Ripple

 

Conclusion:

The Zalman ZM850-HP PSU is currently the largest PSU from Zalman.  While it promises to be quiet, it is a bit weak for today's high-end systems and seems to struggle a bit when forced to run a fairly heavy load.  That being said, it was always within its rated specifications, but we saw fairly large variability at higher loads.  If the trend continued up to 800W+, we could expect to see some rails out of spec.

This PSU is not a write-off by any means though.  It kept our system running solid for days of full-load (650W) testing.  Never once did we have system instability or issues of any kind.  To top it off, it's quiet - super quiet.  With the fan spinning at less than 800rpm, it really adds no noise to your system and is a great choice in a high-end HTPC or any mid to high end system that requires near silent operation.

Pros:

  • Very quiet PSU
  • 14cm fan & heatpipes keep things cool
  • Lots, I mean lots of connectors
  • Stable under hefty load 

 

Cons:

  • Ripple of 12v lines is fairly high at medium load
  • Half-modular design


Because of the high ripple and noise at a 650W load, I can't award this unit a Top Pick, but it deserves to be looked at if you're building a system that requires a good PSU that is very quiet.  For the price though, I can't help but think there are better PSU's for the money.

BCCRating

I'd like to thank ZalmanUSA for sending over this unit for us to review.  It's been a good unit to test out some 8800GTX SLI on a large display and showcase our test rig at a gaming conference.  Please post your thoughts and comments regarding this review in our forum at the "Comments" link below.