Sometimes big things come in small packages. In today's review, a small thing comes in a large package. A VERY large package. How large, you ask?
The Corsair AX850 power supply comes in a box that is 15.5" long. That's 390mm! One would think that with a box this large, there must be something large inside. Certainly, more than just a power supply. Perhaps every Corsair AX850 comes with a 6GB kit of Dominator GT DDR3 memory and a 128GB Voyager thumb drive? Oooh... one could only hope.
Well, before we crack the seal on this box and see what's actually inside, let's see what kind of propaganda Corsair puts on all of this real estate.
In five languages, I am told that this in a high-performance ATX power supply.
On the back of the box, again in five languages, I am given quite the back story:
Wow! Talk about setting the bar high. "Mission-critical stability", "one of the best", "90% efficiency at 50% load".... That's why we're here today folks!
Way in the lower right hand side of the back of the box, we have the DC output capability of this power supply....
| Corsair | +3.3V | +5V | +12V | -12V | +5VSB |
| 25A | 25A | 70A | 0.5A | 3A | |
| Max Power | 125W | 840W | 6W | 15W | |
| 850W | |||||
Along the top of the back of the box, we are told what kind of connectors to expect inside. This is important for those who might have a dual processor board that requires both 8-pin and 4-pin or two 8-pin CPU power connectors or two 300W PCI Express graphics cards that will require four PCIe connectors, two of which will need to be 8-pin PCIe power connectors:
We'll cover all the cables, connectors, their lengths, etc. on the next page once we open this box up. Let's keep looking around this huge box we have here....
On the side of the box, we're given a few more bullet-points and some nifty logos...
Once again we're reminded that this PSU should have mission-critical stability. Apparently, the flexibility is unprecedented due to the 100% modularity. Hmm... Unprecedented means "without previous instance; never before known or experienced; unexampled or unparalleled." I guess all those fully modular Ultra Products and SilverStone power supplies were overlooked when looking for prior art. And now that BFG is out of business and can no longer support their Lifetime Warranty, Corsair does have industry leading warranty and support with it's 7 year warranty.
The logos represent Corsair's 7 year warranty, that the PSU is certified by 80 Plus to perform to 80 Plus Gold standards, that the PSU meets the requirements of the E.U. for an Energy Using Product (EuP) and finally... this unit is ready to be installed in a sixth generation Corvette. Wait... what?
This one actually required an email to Corsair as I have never heard of "C6 Ready" or have seen a "C6 Ready" logo. As it turns out, the C6 Corsair is referring to is the C6 state of an Intel processor, also known as the deep power down state. The C6 state reduces the CPU's core voltage and shuts off power to the core clock and cache thus reducing power consumption. What Corsair means by "C6 Ready" is that even in this power state, which results in a very low load on the power supply, the power supply will still put out voltages that are within specification. I'm sure there are some power supplies out there that might not be C6 ready... right? But I digress...
Finally, from the other side of the box:
Naturally, this PSU has auto-switching circuitry that provides a wide range of AC input, it supports ATX12V 2.3 and EPS12V 2.91 (needs two usable CPU power connectors) and is backwards compatible with older ATX12V specifications. Finally, the dimensions of the unit. 150mm x 86mm x 160mm. Wait? 160mm deep? That's really small... and less than half the size of this box! Well... we know that it's not the PSU taking up all the space in this box. Let's open it up and see what's inside.
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Hmm... it looks like the power cable, a bag of modular cables and an accessory pack take up 1/3 of the box while the other 2/3 of the box is a giant chunk of foam with a manual placed on top.
Lifting off the top half of the foam exposes a bag containing the power supply. Here we can see that the foam is VERY thick, providing more than adequate protection for the power supply.
It's interesting that Corsair went with so much foam in this box. On one hand, the unit is definitely protected and perhaps this will reduce failures caused by rough handling once deployed into the field. But the product manager side of me is concerned with shipping costs and how few units you can put into a master pack and how few units will fit on a pallet. I would expect these increased shipping costs trickle down to the retail price the end user pays.
Once everything is unpacked, we can see our AX850 power supply unit, the manual, a pack of zip-ties, a case badge, four mounting screws, a power cord and a nylon bag with all of our modular cables.
Here is a closer look of those accessories.
Opening the nylon bag exposes a hodge podge of modular cables. Some cables are sleeved while others are the flat type of cables like those used on the HX power supply. With the HX power supply, all of the modular cables were flat while the fixed cables were sleeved. This was unfortunate because the cables typically routed underneath the motherboard would be the 24-pin ATX and the 4-pin or 8-pin CPU power connector, and having these cables flat helps routing these cables between the motherboard and motherboard tray. It is understandable why Corsair would not make the fixed cables the all black flat type like the modular ones. Without having the wires color coded, labor and quality control becomes difficult because the workers cannot differentiate the different voltage wires that need to be soldered down to the PCB. With the AX being fully modular, they have the opportunity to make all of the cables flat and easier to route, but instead, the 24-pin ATX and 4-pin and 8-pin CPU and PCIe power connector cables are all still the usual sleeved type. Hmm... what a shame.
Here is the 24-pin power connector and two 4+4-pin CPU power connectors. As you can see, all three are sleeved.
Here are our two PCIe power cables. Each has a 6-pin and 6+2-pin PCIe power connector. Instead of doing the usual 550mm of cable, one connector and then a second connector 150mm later down the line, the AX850 employs two 600mm coming out of one connector. This means that if you only use one of the two connectors, you have a 600mm long cable that you need to hide. Then again, if you're not using at least two PCIe power connectors, you don't need an 850W power supply.
And here is our assortment of flat modular cables: all peripheral and SATA.
Floppy power is derived by using the included peripheral to floppy adapters.
Below is a table showing all of the included cables and the lengths of those cables, as well as a recap of the unit's dimensions:
| Type of connector: | Quantity: |
| 24-pin ATX connector (600mm) | 1 |
| 4+4-pin ATX12V/EPS12V (600mm) | 2 |
| PCIe (600mm) | 4 |
| SATA (2 cables w/ 2 connectors each) (450mm+150mm) | 4 |
| SATA (2 cables w/ 4 connectors each) (400mm+150mm+150mm+150mm) | |
| 5.25" Peripheral Power Connector (2 cables w/ 4 connectors each) (400mm+150mm+150mm+150mm) | 8 |
| 3.5" Drive power adapter (+100mm) | 2 |
| Unit Dimensions(L x W x H) | |
| 160mm x 86mm x 150mm | |
Now let's have a closer look at the unit itself before we plug it up to the load tester and see how it performs.
In the above two photos we can see that the AX850 has a relatively compact size. 150mm x 160mm is as small as you can get and still use a 140mm fan. Ironically, this unit actually uses a 120mm fan instead.
Here we can see the modular interface of the AX850. The holographic sticker in the upper left hand corner shows that the licensing fee has been paid to Ultra Products for their patent on computer power supply modularity.
Finally, here is a shot of the back of the unit. As we can see, it's a honeycomb-style exhaust vent and we have an on/off switch. Now let's move on to the load testing.
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All testing is done using an SM-8800 active load tester in a 20°C room. Artificial static loads are placed on each rail, then voltages and total wattage is recorded. The loads represent a +5VSB only load, 10%, 20%, 35%, 50%, 65%, 80% and 100% as well as two cross-loads: High +12V and high +3.3V & +5V. The amount of wattage being pulled from the wall is also recorded and efficiency calculated. I also record the power factor of the unit. This particular unit has no -5V rail and we do not load test the rarely used -12V rail, so there are no results for those two rails.
Test 0 is the PSU in it's soft off mode with only a 2A load on the +5VSB. This test will show us the PSU's standby efficiency. Test 1 is the same as test 0, but we've turned the PSU on. Test 2 through 8 are our progressively increased loads (10% to 100%) and test 9 and 10 are our crossloads.
Temperatures are measured at both the intake fan and exhaust grill of the PSU.
| Corsair AX850 COLD load tests | ||||||||
| Test # | +3.3V | +5V | +12V | +5VSB | DC Watts/ | Eff. | Power | Intake/ |
| Simulated system load tests | ||||||||
| Test | 0A | 0A | 0A | 2A | 5W/ | 81% | .46 | 25°C/ |
| N/A | N/A | N/A | 5.06V | |||||
| Test | 0A | 0A | 0A | 2A | 10.1W/ | 46.1% | .81 | 25°C/ |
| 3.38V | 5.02V | 12.17V | 5.06V | |||||
| Test | 1.5A | 2A | 5A | 2A | 85.7W/ | 82.3% | .96 | 25°C/ |
| 3.37V | 5.01V | 12.14V | 5.05V | |||||
| Test | 2.5A | 4A | 11A | 2A | 171.5W/ | 86.7% | .98 | 25°C/ |
| 3.35V | 4.99V | 12.13V | 5.03V | |||||
| Test | 4A | 7A | 20A | 2A | 299.9W/ | 89.5% | .99 | 27°C/ |
| 3.33V | 4.97V | 12.07V | 5.02V | |||||
| Test | 5A | 10A | 29A | 2A | 425.2W/ | 89.4% | .99 | 21°C/ |
| 3.31V | 4.95V | 12.05V | 5.00V | |||||
| Test | 6.5A | 13A | 38A | 2A | 551.3W/ | 88.5% | .99 | 21°C/ |
| 3.29V | 4.93V | 12.01V | 4.98V | |||||
| Test | 8.5A | 15.5A | 47A | 2A | 674.7W/ | 87.3% | 1.00 | 22°C/ |
| 3.28V | 4.92V | 11.95V | 4.97V | |||||
| Test | 9A | 18A | 60A | 2A | 839.4W/ | 85.6% | .99 | 22°C/ |
| 3.26V | 4.90V | 11.94V | 4.95V | |||||
| Test | 15A | 15A | 2A | 0A | 148.4W/ | 82.5% | .98 | 22°C/ |
| 3.32V | 4.96V | 12.13V | 5.09V | |||||
| Test | 0A | 0A | 70A | 0A | 830.3W/ | 86.8% | .99 | 22°C/ |
| 3.29V | 4.94V | 11.93V | 5.03V | |||||
First observaion is test 0 which shows very good efficiency while the unit is in standby.
Going across the columns of the table for cold loads, we find that the 3.3V dropped 3% going from 10 to 100% load. +5V dropped almost 2.5%. This isn't too bad, especially considering that this unit uses DC to DC for the +3.3V and +5V. +12V, on the other hand, barely dropped 2%.
If we look at test 3, 5 and 8 (20%, 50% and 100%), we can see that we just missed the 80 Plus Gold criteria (87%, 90%, 87%) with this unit. Instead, we have very respectable silver performance. The numbers are so close, it's barely worth mentioning. Different variables come into play that could cause the efficiency to be slightly different between my unit and the one that 80 Plus tested, such as how the loads are distributed across the rails or how well the connection is between the modular cables and the PSU body or the connection between the connectors and the load tester itself.
One thing to note is a strange electrical noise I heard during test 3. Once I proceeded to test 4, the noise went away. A second sample provided by Corsair exhibited no such noise.
Another thing to note is that the fan does not spin on this unit until temperatures reach a certain point. For me, the fan didn't start spinning until test 5, and this can be seen in the temperature results. As the fan began to spin, it pulled in more of the room temperature air, dropping the intake temperatures, and increased the exhaust temperatures. The fan was barely audible, especially over the roaring noise of the SunMoon's exhaust fan. By test 8, the fan seemed to step up to an audible level, but nothing in the least bit annoying.
Cross load results were very acceptable. Not that such loads are realistic, but because this unit is essentially a +12V PSU with DC to DC modules regulating the +3.3V and +5V, cross loading results are expected to be uneventful.
Let's see what the oscilloscope has to show us...
|
Oscilloscope Measurements for Corsair AX850 | |||||
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Test # |
+3.3V |
+5V |
+12V |
+5VSB | |
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Test 1 |
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Test 2 |
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Test 3 |
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Test 4 |
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Test 5 |
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Test 6 |
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Test 7 |
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Test 8 |
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Test 9 |
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Very clean voltage here. One would say "uneventful" if it weren't for that +5VSB. What the heck is that thing doing? Each test produced a different waveform even though the load is 2A on all but the crossload tests. And then, during the crossload tests, when there's no load on the +5VSB, there's a different wave form depending on the crossload. With all of the load on the +12V, the +5VSB waveform is down right out of control! Very strange.
Now for the hot load tests....
Hot loads are produced by pumping the hot air produced by the load in the load tester into the intake of the power supply:
| Corsair AX850 HOT load tests | ||||||||
| Test # | +3.3V | +5V | +12V | +5VSB | DC Watts/ | Eff. | Power | Intake/ |
| Simulated system load tests | ||||||||
| Test | 0A | 0A | 0A | 2A | 10.1W/ | 47.6% | .80 | 26°C/ |
| 3.38V | 5.02V | 12.19V | 5.06V | |||||
| Test | 1.5A | 2A | 5A | 2A | 85.8W/ | 83.4% | .96 | 26°C/ |
| 3.37V | 5.01V | 12.16V | 5.05V | |||||
| Test | 2.5A | 4A | 11A | 2A | 171.6W/ | 86.8% | .98 | 26°C/ |
| 3.35V | 5.00V | 12.12V | 5.04V | |||||
| Test | 4A | 7A | 20A | 2A | 299.8W/ | 89.6% | .99 | 26°C/ |
| 3.33V | 4.98V | 12.07V | 5.02V | |||||
| Test | 5A | 10A | 29A | 2A | 425.5W/ | 89.6% | .99 | 30°C/ |
| 3.32V | 4.96V | 12.05V | 5.00V | |||||
| Test | 6.5A | 13A | 38A | 2A | 551.6W/ | 88.7% | .99 | 32°C/ |
| 3.30V | 4.94V | 12.01V | 4.99V | |||||
| Test | 8.5A | 15.5A | 47A | 2A | 675.2W/ | 87.9% | .99 | 33°C/ |
| 3.28V | 4.92V | 11.97V | 4.97V | |||||
| Test | 9A | 18A | 60A | 2A | 840.4W/ | 86.3% | .99 | 35°C/ |
| 3.26V | 4.90V | 11.94V | 4.95V | |||||
| Test | 15A | 15A | 2A | 0A | 148.5W/ | 82% | .98 | 34°C/ |
| 3.32V | 4.96V | 12.15V | 5.09V | |||||
| Test | 0A | 0A | 70A | 0A | 831.9W/ | 86.8% | .99 | 35°C/ |
| 3.30V | 4.94V | 11.89V | 5.03V | |||||
Well that's interesting! It seems that some of my efficiency numbers have gone UP! Hmm.... I guess the AX850 needs breaking in just like a high performance racing engine. I still didn't hit 80 Plus Gold, though.
Now that we've wrapped up the load tests, let's open up this beast and have a look inside.Page 4 -
19 screws hold this power supply together... NINETEEN SCREWS! Sure, four hold the modular PCB to the housing, but NINETEEN SCREWS!
Once disassembled, we can see that the Corsair AX850 is based off the Seasonic X-Series power supply.
The first thing you'll probably notice here is that the unit almost completely lacks wires. This is because +12V only connectors, like PCIe, ATX12V, and even the +12V wires that go to the 24-pin power connector, are all fed directly to the modular connectors soldered onto the PCB. Then there are only a handful of +12V wires going to a PCB that has the DC to DC converters as well as modular connectors for peripheral, SATA and the remaining 24-pin power wires on it.
First, our line power goes through a Delta EMI Filter...
After this stage, we go to a typical, albeit stout, transient filter stage.....
In the middle of the above picture, we see our X capacitor, in the lower left we have our two Y capacitors, and located just above the ferrite coil to the right, we have an MOV. There is also a relay in the area of the power supply.
The way this relay is utilized is pretty clever. A thermistor is used in series with the AC input. This thermistor is used to measure and protect against inrush current. Once the PSU is already up and running, the relay is energized and the path to the thermistor is cut off. This increases efficiency by not including the thermistor in the primary circuit.
After this stage, we get to our rectifying stage. To the far left of this same photo, we see two GBJ1506 rectifying bridges screwed to a heatsink.
Three Infineon 6R160C6 power MOSFET's are used on the APFC circuit. The diode is an STPSC806D. The switching transistors used as the main converter is located on the reverse side of this heatsink and are two more of the 6R160C6 MOSFET's
Filtering is done by a pair of Chemi-Con 420V 390uF capacitors rated for up to 105°C operation. Located on a small PCB just next to these capacitors is an IC for controlling the APFC circuit, which is an On Semi NCP16543.
This power supply uses a Champion Micro CM6901 resonant mode controller. Using an LLC resonant topology improves efficiency by changing the switching frequency in response to changing loads.
Speaking of resonant mode controllers.... because the +5VSB is essentially a separate power supply within the power supply, it needs it's own controller. Here, Seasonic uses an Infineon ICE2QR4765 controller.
Now moving to the secondary side of this power supply, things start to really get fun!
Typically, one would use diodes to rectify voltages, and these diodes would be mounted to the secondary heatsink. But this unit uses a set of four Infineon 031N06L MOSFET's.
Add to this that they are mounted to the bottom of the PCB!
Add to this that the heat from the MOSFET's package is dissipated by the power supply housing!
Add to this that shining a light through a prism onto this power supply reveals the image of a unicorn. Ok... maybe not.
The filtering of the +12V is handled by a number of capacitors, mostly solid state capacitors, located in the very middle of the board.
At the top of the above photo, you can see where the row of +12V only powered modular connectors are soldered directly to the board. This completely eliminates any DC wires inside the unit, outside of those delivering +12V power to the DC to DC converters.
For +5V and +3.3V output, Seasonic uses DC to DC converters mounted to the modular PCB.
This part of the power supply uses an APW7159 IC while four Infineon 060N03L power MOSFET's regulate the +5V output and four more of the same power MOSFET's regulate the +3.3V.
The filtering stage for the +3.3V and +5V are on the other side of the modular PCB...
The supervisor IC used on this unit is the Silicon Touch PS223. It's responsible for OCP, OVP and UVP.
Finally, the fan that keeps all of these components cool is a Sanyo Denki San Ace 120 double ball bearing fan.
In the above picture, you can see a primitive baffle is used to force the air towards the front of the PSU so it doesn't all immediately escape out the back. It's not as fancy as some baffles I've seen, but I'm sure it gets the job done.
Well... That was a hell of a break down. Let's go ahead and score this thing now.Page 5 -
Power supplies at jonnyGURU.com are scored in four categories: performance, functionality, value and aesthetics. Each category has a different weight that effects the overall score.
Performance (40% of the final score) - The AX850 really performs well. Voltage regulation was good, efficiency was excellent, albiet not to Gold standards in my unit, the fan produced virtually no noise and, other than some funky waveforms coming from the +5VSB, ripple suppression was fantastic. 9.5.
Functionality (20% of the final score) - You can't knock a PSU for being FULLY modular at all. My compaint was the mix of flat with sleeved cables. Some people like the flat cables, while others like the sleeved cables. Something bothers me about the mixing of the two. The PSU is compact, so that's a plus and they include an on/off switch on the back, which is also a plus. I feel comfortable giving the unit a 9.5 here too.
Value (30% of the final score) - The AX850 typically sells for around $189.99. This is rather expensive for an 850W power supply. There are other 80 Plus Gold modular power supplies for less. That said, this PSU is not, by any means, a "cheap" power supply in build quality. I'm going to be fair here and give this PSU an 8 for value.
Aesthetics (10% of the final score) - This unit has very tame looks. It's a flat back finish with "Corsair AX850" stickers on each side. Nothing too flashy, but sometimes that's a good thing. I think the biggest aesthetic anomaly here is the hodge podge of cables. I'm going to give this unit an 9 for aesthetics.
When we put this all together, we get a total score of 9, and thus the unit gets a "jonnyGURU recommended".
| Performance | 9.5 |
| Functionality | 9.5 |
| Value | 8 |
| Aesthetics | 9 |
Total Score | 9 |
Summary
Computer power supplies have come a long way in just the last couple of years. With the implementation of resonant mode topologies and DC to DC converters for non-primary DC output, we've seen efficiency increase more and more. The AX850 is an example of how to implement these features as effectively as possible by avoiding the high ripple typically associated with resonant mode topology and the poor voltage regulation typically associated with DC to DC converters under load. The cost is high, but you get what you pay for.
The Good:
- Efficiency just below 80 Plus Gold
- Quiet, especially when the fan didn't spin at all!
- Decent voltage regulation
- Fully modular
- Good ripple suppression
The Bad:
- Nothing really bad to say here.
The Mediocre:
- The price is high... but you get what you pay for!
- Hodge podge of modular cables. Some sleeved... some flat.
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