Our load tests utilize a couple of FAST ATE active load testers and a variety of other equipment such as an oscilloscope, power conditioner, temperature probe and a power consumption meter. You can read more about our standard testing approach here.
The tests performed are based around six conceivable setups that are out there and progressively load down the PSU up to the power supply's limits or 1000W, whichever comes first. Since our test equipment's great than that of the OCZ ZX 850, we can test it to the maximum.
After throwing the OCZ ZX 850 power supply through our gauntlet of tests, we were left with a solid set of numbers out of the PSU. Most impressive were the 3.3V and 5V rails. They proved to be rock solid throughout all of the load tests we threw at the OCZ ZX 850. The 3.3V rail didn't budge the entire time and the 5V rail stayed within 1% regulation the entire time. Voltage readings from the 12V rail were excellent as well which stayed within 1% throughout all of the tests. The 12V rail did show the largest delta of our voltage readings, but it is still well within ATX specifications.
Ripple on the 12V rail was also excellent. In Test 1, noise on the 12V rail came in at a barely noticeable 8mV peak to peak. This increased slightly in each test as loads were increased, finally settling at 21mV peak to peak. This is quite clean for a 12V rail under full load.
As far as efficiency is concerned, the OCZ ZX 850 achieves its 80Plus Gold rating that it is certified for. In order to receive an 80Plus Gold rating, a power supply must be 87%, 90%, and 87% efficient at 20%, 50%, and 100% loads respectively. The ZX 850 starts out well above the mark, but at the end it is cutting it close. It would be nice to see efficiency a little higher under full loads, especially since OCZ markets this power supply towards gamers and enthusiasts alike of which are constantly pushing their systems to the limit.
Taking a look at the voltage results, we see some rather impressive results for quite a heavy load. The AX1200 manages to maintain regulation on the 3.3V rail within 2% during the tests up to 1000W. The 5V rail manages a little better and stays just within the 1% regulation range. The single 12V rail manages 2% voltage regulation as well. While we have seen better voltage regulation out of other power supplies in the past, we haven't seen anything better out of power supplies of this caliber.
OCZ has brought an excellent power supply to the market with the ZX 850. That said, we have a few minor discrepancies with the ZX 850. First is the lack of being rated for 100% continuous output at 50C. This should be considered a staple of any power supply that is meant for gamers and/or enthusiasts as they are often the ones putting the power supply under these conditions. Short of the cheaper capacitors used in the build of the ZX 850, the power supply has great build quality. Lastly, it would be nice to see a little more efficiency out of the unit under full loads.
These are of course minor issues with the ZX 850. Throughout all of our tests, the ZX 850 performed quite well and exactly as advertised. Voltage readings were excellent all the way through and the ripple we saw on the 12V rail was equally impressive. Perhaps what sweetens the deal even more is the price. At $169.99, it is one of the cheapest 850W Gold rated power supplies on the market and arguably is more feature rich than the competition with the inclusion of fully modular cables.