We were really curious to see how much power this unit could really deliver, because by the project used we suspected it could deliver far more than what was labeled.
We tried to see not only the maximum power we could extract from this power supply with it still working inside its specs, but also if all its protections are working correctly. As you know by now, power supplies usually burn when we try pulling more than it is capable of handling if it doesn’t feature overload protection (OLP or OPP; these two acronyms mean the same thing).
The first thing we like to do is to test if over current protection (OCP) is active and at what level it is configured. Inside the power supplies all +12 V rails are connected together and the difference between them is that each group of wires uses a separated OCP circuit. We’ve seen lots of power supplies with their OCP configured with values higher than what was printed on the power supply label, or simply disabled, what transforms the power supply into a single-rail unit.
To test this feature we removed all power supply cables from our load tester leaving only the main motherboard cable. Then we increased current on +12 V until the power supply would shut down. On OCZ StealthXStream 600 W this happened when we tried to pull more than 18 A, which was a miracle: this is the first power supply we’ve seen with its OCP circuit configured with the exact value that was printed on the label. Usually on power supplies that have their OCP circuit correctly configured, the manufacturer sets this circuit at 1 or 2 amps above what is written on the label.
Then from test number five presented on previous page, we started increasing currents to see the maximum amount of power we could extract from this power supply before it would shut down (if it implements any kind of overload protection) or burn (if it doesn’t).
We were happy to see that this power supply doesn’t turn on if you try to pull more power than it can deliver – funny enough the manufacturer doesn’t list overload protection (OPP or OLP; these two acronyms mean the same thing) as a feature for this power supply. The maximum amount of power we could pull from this unit is described below.
Input | Maximum |
+12V1 | 26 A (312 W) |
+12V2 | 26 A (312 W) |
+5V | 10 A (50 W) |
+3.3 V | 10 A (33 W) |
+5VSB | 3 A (15 W) |
-12 V | 0.5 A (6 W) |
Total | 728.8 W |
% Max Load | 121.5% |
Room Temp. | 47.9º C |
PSU Temp. | 53.6º C |
AC Power | 920 W |
Efficiency | 79.2% |
Under this test all outputs were within specs and noise level at +12V1 input from our load tester was at 86 mV, at +12V2 was at 74.8 mV, at +5 V was at 28 mV and at +3.3 V was at 39 mV.
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Figure 19: Noise level at +12V1 input from our load tester with power supply delivering 729 W.
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Figure 20: Noise level at +12V2 input from our load tester with power supply delivering 729 W.
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Figure 21: Noise level at +5 V with power supply delivering 729 W.
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Figure 22: Noise level at +3.3 V with power supply delivering 729 W.
Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.
When the power supply fan is running slowly it is really quiet, but as soon as it starts spinning at its full speed – which happens when the power supply temperature reaches 30º C – noise level becomes somewhat high.
