CoolerMaster 850W Real Power Pro PSU - PAGE 4
J. Micah Grunert - Wednesday, December 13th, 2006

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I guess it would be a good idea to make sure that the Cooler Master 850W Real Power Pro lives up to its expectations. And we have a couple of methods for doing so. First, I'll take some sound measurements to see how quiet (or how loud) the unit is. It's a pretty simple task. Just find the quietest atmosphere possible and jumper the power supply to life. Then take a couple readings with our Omega HHSL1 sound meter. As for our quite place, I have a bathroom at home can can get down to 28 dbA ambient in the middle of the night. That's more than quiet enough for some accurate sound measurements.

But there was a problem, a little buzzing problem. When I had plugged in our RS-850-EMBA there was this buzzing sound. So, I unplugged it and the buzzing sound persisted until the residual charge in the capacitors had drained away. Once the supply had been completely discharged, it was silent. This buzzing sound, somewhat akin to a mosquito wisping around a quiet room, could only be one thing. There is something loose inside our Cooler Master 850W supply.

Now when I say loose, I don't mean something I can tighten down with a screwdriver. I mean a component that has a notable manufacturing defect. A potential culprit could be one of the three transformers. If one of the steel plates that comprises its body is loose, it will vibrate back and forth with the frequency of the magnetic field generated. All electrical transformers create magnetic fields. And if this magnetic field is constantly fluctuating at 60hz, or 60 cycles per second (household AC current frequency), then a loose metal plate in a transformer may begin to vibrate like a saxophone reed. There may be the off chance that it could be another component that's creating the buzzing sound, but my money is on a bad transformer.

This doesn't necessarily mean that the Cooler Master 850W will fail prematurely or will have problems delivering the juice it promises. It just means you'll have to live with this little buzzing sound coming from your rig, and honestly it isn't that bad. My sound testing was done with the power supply suspended from a wall hook, just to try an eliminate the possibility or any vibrations from the fan. Here's a quick little chart to show what audible effect that buzzing sound had.

 

Cooler Master RS-850-EMBA Ambient Sound Testing
Ambient Noise Level	28.8 dBA
10cm Distance with Supply Buzzing but Fan off	29.9 dBA
1m Distance with Supply Buzzing but Fan off	29.3 dBA

No just to confirm. As I had mentioned earlier, the buzzing sound will persist until all of the juice in the capacitors has been drained. My ambient reading of 28.8 dBA was taken at 2:30 in the AM with the supply still in its box. I had also used an LED lamp instead of the compact fluorescent bulbs in my bathroom at home. On of the fluorescent bulbs creates a noticeable buzzing sound itself. It's probably on its last leg and should be replaced. So I had an extremely quiet environment for testing with absolutely no sounds polluting my readings. Then, I plugged in the Cooler Master 850W and quickly unplugged it again. The buzzing sound persisted for maybe 20 seconds afterwards until the capacitors had drained.

Now these aren't the final sound measurements. These are just an indication of what the ambient noise level of this particular supply will be when it's plugged in. It will be totally silent if left unplugged of course, but most of us tend to leave our power supplies plugged in all the time. Again, this sound, though small, is some what irritating. Granted, once you drop this supply into a case and push it under a desk the buzzing sound should be hardly noticeable.

But now we should test the Cooler Master 850W with the fan running. Of course it's going to be louder, and that persistent buzzing sound will add to the overall noise level. But again, all of our sound level testing is done with the supplies outside of the case. It would be a totally different story if we had to take sound measurements with the supply inside a case. And there is also the added difficulty of selecting an enclosure that would approximate the sound dampening properties of every case on the market. Never the less, here's the figure I pulled.

I was surprised! I thought that buzzing noise would have thrown the Cooler Master RS-850-EMBA sound measurements for a loop. I guess it can be expected that we pulled off some low dbA readings. For one, the big 120mm fan in our Cooler Master 850W looks to be of top quality. That helps to keep the noise level down. Second, high frequency sounds don't travel very far. Their very narrow sign wave breaks down quickly. A simple fact of acoustics and audio engineering is that lower frequencies travel farther. Higher frequencies don't travel very far at all. It's nice to see that the Cooler Master 850W is a quiet supply, despite that little buzzing problem.

Now that we have sound testing out of the way, we move onto the voltage testing. For this we use the one item known to man that will test a power supply like no other. Well, it's actually two things in the form of a pair of CrossFire cards. As legend has it, graphics enthusiasts began seeing problems with their power supplies and CrossFire equipped rigs several months ago. Turns out that CrossFire sucks up an extraordinary amount of juice compared to other graphics cards. If you don't have a CrossFire Certified supply running your CrossFire enabled cards, chances are your system will crash during game play. And worse yet, your power supply may die. So, we'll be using our trusted old video test bench rig to test the Cooler Master RS-850-EMBA. Here's the skinny on what parts we used.

Test Setup

• Thermaltake Toughpower 750W cable management
• AMD Athlon 64 3700+ processor
• Asus A8R32-MVP Deluxe mother board 
• 2 x 512 MB OCZ Platinum PC4800 memory
• Seagate Barracuda 7200.9 SATA hard drive
• Samsung WriteMaster DVD burner
• Windows XP Professional SP2

And the CrossFire cards we used

• 2 x ATI Radeon X1800 XT CrossFire

All of the following tests we preformed while running 3DMark 2006 with 2 instances of CPU burn-in running in the background. This should more than sufficiently load up both of the ATI GPUs and both cores of our processor. And one more note with one of the supplies tested. With the ThermalTake Toughpower 750W cable management supply we had also tested the connectors at the bus bar on the side of the power supply. The reason for this being that adding connections to a circuit will create some noticeable measurement of resistance. Granted, these differences we found were so negligible that they won't make any real difference. They're just there because I felt it to be important. All of the other measurements were taken from the first connector on the 24 pin motherboard power connector and the first Molex plug on the power cables. Fortunately, there was no difference between the voltage measurements at the cable ends or the 24 pin connector. The only exception being that of the 3.3V voltage rail which we could only take from the 24 pin mother board connector.

To measure the respective voltage rails we used our Mastercraft 052-0060-2 volt meter. This little tools lets us test for voltage, resistance and amperage. Though we're only interested in the voltage readings in this case.

Voltage testing with 3DMark 2006 & CPU burn-in times 2 (error checking removed)

Cooler Master RS-850-EMBA

850W Power Supply

 

	3.3 Volt Rail	5 Volt Rail	12 Volt Rail
Idle	3.32 Volts	4.99 Volts	12.10 Volts
Load	3.31 Volts	5.015 Volts	12.105 Volts

 

 

 

The figures don't lie! The Cooler Master RS-850-EMBA is incredibly stable. Granted, the other supplies in this round up are quite stable as well. But I would prefer to have a power supply that puts out he juice at the voltage stated, and not too far off from that. As you can see, The Cooler Master 850W is near dead on accurate for the 3.3V and 5.0V rails and kicks up only slightly on the 12.0V rail. A boost of 0.1V on the 12V isn't much to worry about. But if we look at the AeroCool Zerodba and its 3.3V rail, running at 3.44V at idle worries me. This added voltage could put some amount of strain on the motherboards VCM (Voltage Controller Module). It is wholly preferable to have a supply that puts out 3.3V on the nose, or any other voltage for that matter.

But the sweetest thing of all is how little the Cooler Master 850W fluctuated between idle and load. The difference is a nominal .01 volts or less. Other power supplies would kick up or kick down the voltage by .1 volts on a specific rail in some instances. The only supply in this group that really compares is the Thermaltake Toughpower 750W. It hardly fluctuated at all. These tests are hinting toward the increased voltage stability we'll be seeing with higher wattage power supplies.

The important thing about this rock solid stability is the official certified support for NVIDIA G80 based video cards.  With this type of capacity you could run 2 SLI G80's without problems.  I know NVIDIA doesn't require more than a 550W PSU in a G80 SLI setup but I assure you that there will be many users who are more comfortable with a beefy 850W Real Power PRO powering their G8800GTX rigs.  We only had a single 8800GTS available at time of testing so I didn't do any testing (two CrossFire cards would have greater draw than a single 8800 GTS), but the stability of the CrossFire testing lends confidence of the stability of this PSU under any circumstances.

next: Conclusion »

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