Reviews - Corsair TX850 Power Supply
Sample Provided by: Corsair (By OklahomaWolf on Wed, Dec-17-2008)

Page 2 -

Now we're getting to the good stuff - the load testing. As always, the SunMoon SM-268 will be the Watson to my Sherlock, assisting me in electronically loading the TX850 in a set of three tests. First, I'll do some progressive and crossload tests at room temperature, just to see if the big Corsair can do what it says it can do. Then, I'll run it through a set of specialized overshoot transient tests to see if there are any big turn on spikes or nasty negative voltages that could damage equipment. Finally, I'll repeat the progressive and crossload tests in the hot box, to see if heat can bring it down and whether or not that fifty degree operation promise is attainable.

Now, my loads for the progressive and crossload tests are chosen within the confines of the label's maximum ratings. This is done to avoid overloading any one rail of the unit, and thus painting an unfair picture of the unit's performance. Progressive load tests are done from about 20% to 100% of the unit's full rated capacity. Crossload tests are done first to skew the load towards 3.3V and 5V, to see how stable the unit can hold the voltages for that old Slot A system in the basement; and then towards 12V to see what happens to the voltages when you wake up those two GTX 280 cards on a modern rig.

Enough talk. Let's get the SunMoon in gear and see what's up.

Results from Corsair TX850 COLD load tests
Test # +3.3V +5V +12V DC Watts/
AC Watts
Eff. Intake/
Exhaust
Simulated system load tests
Test
1
3A 3A 12A 190W/
228W
83% 22°C/
27°C
3.35V 5.07V 12.10V
Test
2
5A 5A 24A 352W/
410W
86% 22°C/
31°C
3.34V 5.05V 12.09V
Test
3
8A 8A 36A 521W/
613W
85% 24°C/
36°C
3.32V 5.02V 12.07V
Test
4
10A 10A 48A 681W/
820W
83% 25°C/
41°C
3.30V 4.99V 12.05V
Test
5
12A 13A 60A 849W/
1060W
80% 25°C/
43°C
3.27V 4.96V 12.02V
Test
CL1
21A 22A 1A 212W/
284W
75% 25°C/
41°C
3.31V 4.96V 12.11V
Test
CL2
1A 1A 65A 811W/
993W
82% 25°C/
43°C
3.30V 5.03V 12.04V

And I have some good news for you already, for it seems that the TX850 is able to best its 750W brother in terms of efficiency over the broad range of operating conditions. It starts off higher immediately, at 83%, tops out at an excellent 86%, and only really drops below the TX750 at full power. The platform on which this unit is based tends to reach its limits around 850W, though, so this isn't too big of a shock.

What is a bit of a shock is that this unit is outperforming little brother for voltage stability. 5V regulation isn't quite as good with a 0.11V difference between tests one and five, but for the most part this unit is holding its voltages under tighter rein than the TX750 did. That's awesome. And look at the two crossload tests, CL1 and CL2... as was the case with the TX750, this unit is independently regulated for the extreme differences in loading fail to make it lose its cool.

Time to do the new overshoot transient tests. I didn't have these for the TX750, so I'll be anxious to see what these scope shots look like.

Overshoot Transient Testing - Corsair TX850
VSB On
VSB to Full 12V
Off to Full 12V

Just a quick note on how these tests work. When a switching power supply is fired up first thing in the morning, it doesn't just come up with the correct voltages right away. Due to inherent design issues, they usually produce a brief spike in each output before they go on to produce stable voltages. ATX spec calls for these spikes to be no more than 10% above mean value on all rails, with no negative readings present. Negative readings are very bad. First, I switch on the unit and have the scope watch the fully loaded 5VSB rail for those spikes. Then, I power the unit on to test five's loads while getting the scope to watch the 12V rail. Finally, I use the switch on the back to power the unit on to test five's loads and look at the 12V rail again.

And the good news here is, the TX850 passes all these tests with room to spare. Nothing at all to complain about, except for that small extra spike in the waveform there, and that won't hurt anything. I've seen many units do that.

Time to fire up my modded ATX case I call a hot box and see how this thing does when roasted in the fires of the SunMoon's own not inconsequential heat output.

Results from Corsair TX850 HOT load tests
Test # +3.3V +5V +12V DC Watts/
AC Watts
Eff. Intake/
Exhaust
Simulated system load tests
Test
1
3A 3A 12A 190W/
229W
83% 29°C/
37°C
3.34V 5.07V 12.09V
Test
2
5A 5A 24A 352W/
413W
85% 32°C/
42°C
3.38V 5.09V 12.12V
Test
3
8A 8A 36A 521W/
616W
85% 36°C/
53°C
3.32V 5.04V 12.07V
Test
4
10A 10A 48A 681W/
823W
83% 40°C/
61°C
3.31V 5.02V 12.06V
Test
5
12A 13A 60A 849W/
1069W
79% 45°C/
72°C
3.29V 4.99V 12.04V
Test
CL1
21A 22A 1A 212W/
283W
75% 33°C/
54°C
3.32V 5.00V 12.11V
Test
CL2
1A 1A 65A 811W/
991W
82% 42°C/
66°C
3.34V 5.06V 12.08V

Ok. I have some good news and some bad news. The good news is, there isn't a thing I can do to make the voltages get unstable, even at a 45 degree intake temperature by test five. The bad news is, the hot box has shown that at 850W, the PSH platform really is at the upper limits of performance when the efficiency drops below 80% to 79.4%. I would suggest to you that if efficiency at this power level is really important, take a good look at the HX1000 instead. I mean, that unit was well above 80% at 850W, with even higher intake temps than this.

That said, this kind of performance is certainly nothing to discourage me. It can do 850W when I bring the heat without complaining, so there's nothing I can really complain about either.

Oscilloscope Results - Corsair TX850
Test #
+3.3V
+5V
+12V1
Test
1
Test
2
Test
3
Test
4
Test
5
Test
CL1
Test
CL2

And there's certainly nothing to complain about here, for even the 12V rail is still below 70mV of noise. This is very good for the PSH platform at these power levels, and in fact is again outperforming the TX750, which got up to 100mV. ATX spec is 120mV.

 



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