OCZ ProXStream 1000 W Power Supply Review

Load Tests

We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology. All the tests described below were taken with a room temperature between 45° and 49° C. During our tests the power supply temperature was between 50° and 68° C (we will talk more about this very high temperature level below).

First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load.

For the fifth test, where we wanted to pull 1,000 W from this power supply, we ran into a problem not related to the power supply, but with o
ur load tester. Our tester (a SunMoon SM-268) has two +12 V inputs, each one with a limit of 400 W or 33 A. For this particular test we wanted to pull more than 33 A, but we couldn’t, as we were limited by our equipment. So in order to achieve 1,000 W we had to increase the amount of current (and thus power) we pulled from +5 V and +3.3 V outputs. This wasn’t the ideal scenario (we wanted to put the +12 V outputs at 36 A and the +5 V and +3.3 V outputs at 14 A instead of 22 A) because nowadays a very high-end PC will concentrate its power on +12 V outputs and not on +5  V and +3.3 V. This happens because the video card auxiliary power cables have only +12 V wires, and the reason high wattage power supplies exist is to feed computers with two or more very high-end video cards.

On the other hand we were pulling a total of 66 A (800 W) from the +12 V outputs and the power supply label says the +12 V limit is 70 A (840 W), so we were very close.

In the table below we list the load patterns we used and the results for each load. +12V2 is the second +12V input of our load tester and on this test it was connected to the power supply EPS12V connector, which is the only connector on the power supply +12V1 virtual rail. Keep in mind that power supply uses a multiple rail design with four virtual rails and during our tests the first rail (+12V1) was connected alone to the +12V2 input of our machine, while +12V2 and +12V3 rails were connected together on the +12V1 input from our tester. The power supply +12V4 rail wasn’t connected to our tester, as it has only one video card power connector input. See previous page for more details on how the four rails are distributed on this power supply.

Even though this power supply passed on our load tests, we have some important comments. First our full load test wasn’t done as we liked, as already explained.

Second, this power supply efficiency dropped below the 80% mark on tests four (800 W) and five (1,000 W) and that is the reason OCZ isn’t advertising this power supply efficiency. While when pulling 800 W efficiency was at almost 80% (79.6%) at full load efficiency dropped to 74.5% and we were pulling 1,335 W from the power grid to produce 1,000 W, completely wasting 335 W of power just to have our system running.

Also during our fourth and fifth tests we started hearing a high pitch noise coming from the power supply. We conducted some tests to discover when exactly this noise starts and we found out that whenever you pull more than 22 A from 12 V you will start hearing this noise. It isn’t loud and since at this time the power supply fan will be spinning at its full speed anyway – making a lot of noise –you won’t hear it.

But the greatest problem with this power supply was its temperature. We suspect that because of its reduced size and the use of an 80 mm fan – which is too small for a 1,000 W power supply – this unit would overheat. Our suspicion proved to be right. With other power supplies we tested the power supply temperature was only one to three degrees Celsius above room temperature – for example, 47° C when the room temperature was 45° C. But with this power supply this didn’t happen. On the first test the difference was of five degrees, on the second test the difference was of four degrees, on the third test the difference was of seven degrees and on the fourth test the difference was of nine degrees. But the real problem was when pulled the full 1,000 W from the power supply: the unit reached 68° C while the room temperature was of 49° C.

Electrical noise was within specs, reaching 68 mV peak-to-peak on +12 V outputs during the fifth test. Some people would prefer to see something below 60 mV here, but we think noise was fine, especially because we were pulling the full 1,000 W from this unit. On lower loads noise was also lower (45 mV with 60% load, for example).

After these tests we tried to pull even more power from OCZ ProXStream 1000 W. The problem was that the +12 V outputs were already maxed out because of the limit of our machinery. So the only option we had was to increase current/power on +5 V and +3.3 V, which would allow us to pull more power from this unit, but wasn’t reflecting the reality, as a high-end gaming PC wouldn’t pull that much from these two outputs. We did this only as an exercise – as we are explaining, these results are flawed as we should had pulled more current from the +12 V outputs.

Below you can see the maximum amount of power we could extract from this unit keeping it working with its voltages and electrical noise level within the proper working range. When we tried to pull more than 24 amps from +5 V and +3.3 V voltages were still within specs, but electrical noise increased to levels we didn’t want. At 25 A noise at +5 V output was at 48 mV, touching the 50 mV limit, so we can’t consider this result as valid since it isn’t safe. And above 25 A noise was above 50 mV. At 24 A noise level at +5 V output was at 22.8 mV peak-to-peak and at +12 V output noise was at 70 mV.

Under this condition the power supply temperature was at 68° C, room temperature was at 52.7° C and we were pulling 1,363 W from the power grid.

Short-circuit protection for both +5 V and +12 V outputs worked just fine, but it seems, however, that this power supply doesn’t have over current protection (OCP), or it is set way over 33 A – while according to the power supply label the limit for each +12 V rail is of 20 A. As you saw we above pulled 33 A from the EPS12V connector which was connected to the +12V2 input of our load tester and the power supply kept working just fine instead of shutting down.

As for the over power protection (OPP) we couldn’t test it because of the 33 A limit of our load tester.

A feature we could see in action was the fan speed changing depending on the power supply temperature. But since this unit works at very high tempe
ratures during our tests its fan was spinning at full speed all the time, producing a very loud and unpleasant noise.