Date:
Thursday , October 08, 2009
Author:
Paul Johnson
Editor:
Kyle Bennett
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OCZ Z Series: Z850M 850W Power Supply Review

Today we see what OCZ means when it says, "True to our enthusiast roots..." OCZ claims ultra-high efficiency and has gotten an 80plus.org Gold Certification. The 850 watt realm has proved elusive for great power supplies. Now to see if this PSU can garner an [H] "certification?"

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Load Testing

For those of you that are curious as to some of the reasoning and equipment behind our PSU testing program here at HardOCP, we have put together a living document that shares a lot of the behind the scenes of the program. The testing we are conducting today is exactly as described in that document and will begin with a range of loads tested at 120v input including our torture test and then move on to the same set of tests at 100v input but without the torture test.

120v Load Testing Results

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Test #1 is equal to approximately 25% of the rated capacity of the OCZ Z850M at 45c. This makes Test #1 equal to 226W by loading the 12v rails to 16a, the 5v rail to 2a, the 3.3v rail to 1a, the +5vsb to 2a, and the -12v to 0.5a. The results of Test #1 are all within specification. The DC output voltages are starting off above nominal with the 12v rail coming in the furthest from nominal at 12.29v. The unit’s efficiency is starting off at 86.59% with an exhaust temperature of 49C. Interestingly, the PF is coming in a bit low for an APFC unit at 0.94.

Test #2 is equal to approximately 50% of the rated capacity of the OCZ Z850M at 45c. This makes Test #2 equal to 440W by loading the 12v rails to 33a, the 5v rail to 4a, the 3.3v rail to 2a, the +5vsb to 2a, and the -12v to 0.5a. Test #2 sees across the board drops in DC output voltages with the 12v rail having the largest drop at 0.09v. The efficiency has moved up to 89.07% with an exhaust temperature of 53C. Additionally, the PF has moved up to 0.97.

Test #3 is equal to approximately 75% of the rated capacity of the OCZ Z850M at 45c. This makes Test #3 equal to 655W by loading the 12v rails to 50a, the 5v rail to 5a, the 3.3v rail to 3a, the +5vsb to 2a, and the -12v to 0.5a. Test #3 sees more across the board drops in the DC output voltages with the change on the 12v rail being larger in magnitude than what we saw in the last test at 0.1v. The efficiency of the unit is off of Test #2's high value here as it hits 88.27%.

Test #4 is equal to approximately 100% of the rated capacity of the OCZ Z850M at 45c. This makes Test #4 equal to 853W by loading the 12v rails to 69a, the 5v rail to 2a, the 3.3v rail to 1a, the +5vsb to 2a, and the -12v to 0.5a. In the final regular test we see across the board drops in the DC output voltages again, however the magnitude of these changes are not as great as they were going from Test #2 to Test #3. We also see the efficiency coming in at 87.04% with an exhaust temperature of 60C.

120v Load Testing Summary

The 120v Load Testing results for the OCZ Z850M were very good overall. The voltage regulation was generally good overall with the 12v rail dropping by 0.26v across 69A of the units 71A claimed capacity. The minor rails also showed generally good voltage regulation with changes that were ~0.08v to 0.09v (including the +5vsb). The biggest point here would be the unit’s efficiency which was generally very high at 86.59% to 89.07%.

Unlike the Seasonic X-750 which hit 80Plus numbers under our higher temperatures, the OCZ Z850M could not quite make 80Plus Gold numbers at 45C. We did run the 80Plus test pattern at room temperature and were able to get 80Plus Gold numbers from one of our samples while the other sample came up just short. As such, the Z850M is 80Plus Gold material but under our more demanding and realistic environment users it takes a very small step back. Keep in mind that we do our testing at a very strenuous 45C ambient where 80Plus does its testing at 25C ambient.

One last item of note is the unit’s low PF values in the first two tests which are interesting for an APFC unit. While these values are below the usual 0.98 to 0.99 we see with APFC units, but users won't really care since APFC is mostly exists to make the power companies life easier with reactive loads.