Corsair HX850W (850w) ATX PSU Page: 1
Introduction & Specs
 
Corsair LogoA little over a month ago Corsair announced two new PSU's to join their extremely popular HX line-up. The HX750 and HX850 are two models designed to bridge the rather large gap between the original HX620W unit released in 2006 and the HX1000W released almost two years later. As anyone who's looked into purchasing a PSU recently will tell you, both of these PSU's are widely regarded as being the best in their class, with Corsair not only using only the best factories to build the units, but also specifying upgraded components and various other modifications to improve their performance. In fact, in the case of the HX1000W, Corsair not only picked one of the best OEM's in the industry (Channel Well Technology), but also conservatively labelled the units 1200w output as 1000w just to ensure flawless results.
 
So today we've been given the pleasure of being one of the first sites in the UK to check out the HX850W. Once again both the HX750W and HX850W models are built by CWT, but in a recent conversation with Corsair they confirmed to us that these units are no 'off the shelf' models. They are instead a completely custom design and specification, built after several months of co-operation between Corsair and CWT. However, before I get ahead of myself and start blurting out all of the juicy details let's check out the specs listed on Corsair's website:
 
- Guaranteed to sustain its full rated wattage at an ambient temperature of 50°C
- Up to 90% energy-efficiency under real-world load conditions*
- Single +12V rail design providing up to 70A
- Multi-GPU ready
- 105°C solid state capacitors
- Active Power Factor Correction (PFC) with PF value of 0.99
- Supports ATX12V 2.3 and EPS12V 2.91 standards. Backwards compatible with ATX12V 2.01
- Auto switching circuitry for universal AC input from 90-264V
- Over Current/Voltage/Power Protection, Under Voltage Protection and Short Circuit Protection provide complete component safety
- Dimensions: 150mm(W) x 86mm(H) x 180mm(L)
- MTBF: 100,000 hours - Safety Approvals: UL, CUL, CE, CB, FCC Class B, TÜV, CCC, C-tick  
 
(Queue Slobber)....Yes, if the specs are anything to go by then the HX850W is certainly going to shape up to be one drool-worthy unit. We have 105c solid state caps, a single +12v rail rated at 70 amps and up to 90% efficiency. Basically everything neccesary to certify the HX850W as PSU porn. Additionally, while I was bashing away at this page Corsair also received word that the HX850W had met 80PLUS Gold Certification. Stellar stuff.
 
However, I'm not going to let these mere words seduce me. After all the proof of a PSU is in the testing. So let's move swiftly on to the next page for a closer look.


Corsair HX850W (850w) ATX PSU Page: 2
Packaging & Appearance
 
If Corsair were entering the competition for who has the biggest box in the 850w PSU category then they would certainly win. Seriously though, Corsair really do know how to package a PSU; and judging by external appearances the HX850W looks like it's been treated to exactly the same packaging as it's bigger brother, the HX1000W. 
 
Corsair HX850 Box Front Corsair HX850 Box Back
 
Corsair HX850 Box Side Corsair HX850 Box Side
 
The front of the box keeps things fairly simple with only an arty farty image of the PSU's modular connector system spanning the length of the box and the model number in a big, bold typeface. Around the back of the box there is yet another picture of the PSU, this time with all of the modular cables plugged in. Several other thumbnail style images are also positioned along the top with some brief descriptions in five main languages below.
 
For those with a thirst for information Corsair have also printed both fan speed and efficiency graphs over to the right that give an overview of the HX850W's performance at various load levels. Finally, at the sides and bottom of the box there is yet more information on the number of connectors provided with the unit, a more detailed specs list and a rail layout chart.
 
Corsair HX850 Box Open Corsair HX850 Box Contents
 
Corsair HX850 Contents Corsair HX850 PSU Wrapped Up
 
And here's how you treat a PSU like royalty...Take one HX850W PSU, place inside a clear plastic bag, follow that with a velour drawstring bag and finally completely encase it in-between two large styrofoam slabs custom moulded to the shape of the PSU. Include a large selection of modular cables in a separate canvas velcro bag and place it all inside a large double walled cardboard box complete with an instruction manual, some screws and a few cable ties. The Queen will approve!
 
Corsair HX850 Bottom Fan Area Corsair HX850 Side View
 
Strip off all the packaging and at first glance you'd be forgiven for thinking that the HX850 uses exactly the same outer casing as the HX1000W. However, with dimensions of 150mm(W) x 86mm(H) x 180mm(L) it's actually a good 20mm shorter than its bigger brother, giving you just that little bit more hope at squeezing it inside that powerful-but-small-lan-rig you've been promising yourself.
 
Some other features do remain the same though. Firstly you get the same durable and slightly coarse black powdercoat finish, which (call me a weirdo) not only looks good but also smells strangely appealing too! And then of course there's the 135mm fan complete with Corsair branded fan grill. Comparing the position of the fan between the HX1000W and the HX850W, it certainly looks like Corsair has done some tweaking, moving it closer to the exhaust area on the HX850W. But then again maybe it's just the shorter length of the unit playing tricks on me.
 
 Corsair HX850 Top Spec Sticker Corsair HX850 Spec Sticker
 
A top-down view of the unit reveals the rather compact specification sticker which has been thoughtfully placed on the area of the unit you are least likely to see with it installed in your PC case. Good thing really as both sides of the HX850W have extremely cool (but probably really cheap) Corsair logo stickers on them which gives the unit a distinguishing look.
 
Corsair HX850 Rear Corsair HX850 Modular Connectors
 
At the rear of the unit, everything is pretty much standard with a normal 'kettle' style mains lead,  power switch and honeycomb mesh exhaust grill. I was sorely disappointed to see that Corsair swapped the absolute monster of a switch used on the HX1000W for the much smaller kiddies science project version, but I'm sure it'll do just fine regardless.
 
Now let's move on to the next page where we take a closer look at the modular features of the unit...and even more importantly, the internals!


Corsair HX850W (850w) ATX PSU Page: 3
Cables, Connectors & Internals
 
The HX850W is fitted with a total of ten modular headers, four of which (the blue ones) are dedicated to PCI-E graphics card power, while the remaining six are for SATA/Molex based devices. Unlike the HX1000W, the HX850W is equipped with a single +12v rail removing the need for any kind of 'layout' sticker next to the modular headers informing users which rail each plug is attached to.
 
Corsair HX850 Modular Connectors Corsair HX850 Modular Connectors
 
In addition to the modular connectors, several cables are hard wired into the unit. These include the ATX, EPS-12v and 2x PCI-E connectors which are pretty much the bare minimum required connectors for powering any PC system. Having these essential cables 'hard-wired' is also a good thing as it not only ensures that critical system components get a good; clean supply of power direct from the PSU, but also avoids potential situations where an ill-fitted modular cable could cause system instability or even kill components.
 
Corsair HX850W Connectors
 ATX Connector Native 1x 20+4 Pin
 EPS-12v / P4-12v Connector(s) Native 1x 4+4 Pin
 Molex Connectors Modular 12x
 Floppy Disk Connectors Modular 2x
 SATA Connectors Modular 12x
 PCI-E Connectors Native / Modular 2x 6+2 Pin / 4x 6+2 Pin
 
 
Corsair HX850w Modular Cables Bag Corsair HX850w Modular Cables
 
Ten modular cables are included inside the canvas pouch which means, yes, you can plug each and every cable provided with the HX850W in at the same time. Not that you'd probably ever need to anyway, unless of course you can find a use for 12x SATA and 12x Molex cables inside your system? No, neither could I - but I'm sure some saddo is going to go out of his way to prove me wrong by sending in pictures of his 24 disk RAID array now.
 
Corsair HX850W ATX Corsair HX850W PCI-E
 
Corsair HX850W PCI-E Corsair HX850W Cables
 
The 24-Pin ATX and 8-Pin EPS-12v connectors both have the ability to be 'broken down' to the older 20-Pin / 4-Pin standards to provide full support for older motherboards. This is also the case for the PCI-E connectors (both hard-wired and modular) which can function in either 8-pin format or 6-Pin format, making the HX850W absolutely perfect for any kind of multi-GPU setup.
 
On thing I almost forgot to mention (which deserves a slap on my wrist because it's so awesome) is the modular cables themselves. As with the rest of the HX line-up Corsair have chosen to construct these cables from an almost 'ribbon cable' style wiring where all of the wires are coloured black and moulded together in a flat ribbon style. This is much better than the traditional sleeving and heatshrink job you see on most modular PSU's and should go a long way to improving the internal appearance of any enthusiasts PC.
 
Corsair HX850W Internals Corsair HX850W Internals
 
And here's the money shots! The internal layout of the HX850W is extremely tidy with a slightly unconventional design PCB in the shape of a reversed 'L'. This appears to have been done so that Corsair could squeeze in an additional primary capacitor at the front of the unit while only having to make a few small adjustments to the modular connector backplane to accommodate it.
 
Corsair HX850W Internals Corsair HX850w Internals
 
Two green transformers sit in the middle of the unit with the larger of the two being responsible for all of the main rails. The smaller one's sole purpose in life is to power the +5VSB rail which is used mainly for USB headers and certain parts of the PC system while in Standby.
 
Either side of the transformers are two thin alumimim blocks used as heatsinks. These differ immensely from the oversized 'finned' heatsinks seen in most other PSU's, which tells me that the HX850W is going to be one extremely cool running unit. Either that or Corsair forgot to install heatsinks and I'm going to get my face burned off!
 
Corsair HX850W Capacitors Corsair HX850W Secondary Caps
 
The primary and secondary capacitors are Japanese manufactured Nippon Chemi-Con KZE's rated at 105°C. The primary caps carry specs of  330uF 420VDC, while the specs of the secondary caps are quite a bit more elusive with the only visible info being 200uF. Regardless, these caps are seriously high quality and should ensure trouble free operation for quite some time in the future.
 
Corsair HX850W DC-DC Conversion Corsair HX850W Model #
 
Nestled in between one of the heatsinks and a bundle of cables are the DC-DC boards. These are responsible for taking the PSU's primary +12v output and stepping it down to +3.3v and +5v rails for the rest of the rails. Several Solid state caps have been used here (in fact the only place in the whole PSU) which is probably more down to space limitations than any kind of quality measures.  Also visible nearby is the PCB model number marked as CMPSU-XXXHX....see I told you this was PSU porn.
 
Corsair HX850W Fan Corsair HX850W Fan
 
Cooling is delivered by a 140mm Yate Loon fan with model number D14BH-12. Specifications taken from Yate Loon's website reveal the fan to be capable of pushing 140CFM at 48.5dBA. Why the HX850W needs a fan with this much grunt is beyond me, but Corsair state that the fan doesn't begin to ramp up until the unit hits 550w. So I'm guessing that at low speeds it may deliver slightly better performance than other models.
 
Now let's move on to the testing and find out if all these fancy components actually result in decent performance.


Corsair HX850W (850w) ATX PSU Page: 4
Simulated Load Testing
 
To provide accurate and consistent results in all of our PSU testing, Overclock3D uses professional grade DC electronic load equipment capable of placing a sustained load of 3690w across a total of six rails (including +5vsb and -12v) on the PSU! This is achieved by using a combination of SunMoon and Analogic electronic load equipment which allow us to adjust amperage loads in increments as small as 0.01A while also measuring voltage and wattage readings on-screen.
 
During today's tests, we will be placing the Corsair HX850W under 25%, 50%, 75% and 100% load levels at both room temperature and inside a hot box regulated to a temperature of around 50°C. Additional 'Cross Load' and a 'Max Load' tests will also be performed under these conditions to simulate how the PSU reacts to heavily uneven loads as well as running above its specified output.
 
Corsair HX850W Results @ Room Temperature
   +3.3v  +5.0v  +12v  +5vSB  -12v  AC Watts /
 DC Watts
 Efficiency  Intake /
 Exhaust
Δ Temp
Test 1
(Low)
4.37A 4.37A 14.00A  0.75A  0.20A  233w /
213w
 91.41% 24.5°C /
25.5°C
1.0°C
3.32v 5.10v 12.20v 5.07v  -11.86v
Test 2
(Med)
8.75A 8.75A 28.00A 1.5A  0.40A  458w /
426w
 93.01%  25.3°C /
26.1°C
0.8°C
3.30v
5.08v
12.18v 5.02v  -11.84v
Test 3
(High)
13.12A 13.12A 42.00A  2.25A  0.60A  684w /
637w
 93.12%  25.5C /
26.2°C
0.7°C
3.26v 5.06v 12.14v 4.98v -11.83v
Test 4
(Full)
17.50A 17.50A 56.00A 3.00A  0.80A 930w /
848w
91.18%  25.5°C /
27.2°C
 1.7°C
3.24v 5.04v 12.14v 4.93v -11.85v
Test 5
(x-load)
17.00A 16.00A 1.00A 0.00A 0.00A  176w /
149w
84.65% 25.0°C /
26.1°C
1.1 °C
3.30v 5.08v 12.20v 5.11v -12.47v
Test 6
(x-load)
 1.00A  1.00A  69.40A  0.00A  0.00A  910w /
850w
93.40%  24.5°C /
26.3°C
 1.8°C
3.29v 5.06v 12.14v 5.06v -13.08v
Test 7
(MAX)
 21.00A  21.00A 73.00A  4.50A  0.60A  1201w /
1084w
90.25%  26.4°C /
28.7°C
 2.3°C
3.21v 5.02v 12.10v 4.85v -12.09v
 
Starting with tests 1-4 (the ones you're most likely to see in real life) the HX850W has left me pretty much speechless. Not only was voltage regulation extremely tight all the way up to 848W load, but the efficiency...DAMN, the efficiency was simply amazing staying above 91% at all times. This clearly also had a knock-on effect on the exhaust temperature of the unit which rarely moved more than 1°C above the Intake temps, showing that there is VERY LITTLE energy wasted inside the HX850W during AC/DC conversion.
 
Moving on to the cross load tests 5 & 6, very little changed in terms of voltage regulation. In both tests the HX850W laughed in my face, keeping all rails totally in check like nothing was happening. Only in Test 5 did the testing manage to chip away at the stellar efficiency of the unit by bringing it down to 84.65%. Seriously though, this is still better than a lot of PSU's can manage on a good day!
 
Finally in test 7 the HX850W was hooked up to both of our load testing machines to try and bring the unit to its knee's. Did I manage it?...did I hell! With 21A on both the +3.3v and +5v rails and 73A on the +12v rail the PSU was still laughing at me while delivering rock solid voltages. That's 1084W by the way, 234W more than what it says on the box!
 
In one last off-the-record attempt to get one over on the HX850W I hit it with everything it could take on the +12v rail. 91 AMPS was the read-out on the load tester before the PSU finally decided safely power off. Even then the voltage readout was 12.12v  right up to the end. Corsair - 1, Me - 0!
 
Corsair HX850W Results @ 50°C
   +3.3v  +5.0v  +12v  +5vSB  -12v  AC Watts /
 DC Watts
 Efficiency  Intake /
 Exhaust
Δ Temp
Test 1
(Low)
4.37A 4.37A 14.00A  0.75A  0.20A  233w /
213w
 91.41% 50.4°C /
49.7°C
-0.7°C
3.32v 5.10v 12.20v 5.07v  -11.86v
Test 2
(Med)
8.75A 8.75A 28.00A 1.5A  0.40A  460w /
426w
 92.60% 51.2°C /
50.8°C
-0.4°C
3.30v
5.07v
12.18v 5.02v  -11.84v
Test 3
(High)
13.12A 13.12A 42.00A  2.25A  0.60A  685w /
637w
 92.99%  51.9C /
52.4°C
0.5°C
3.26v 5.06v 12.14v 4.97v -11.83v
Test 4
(Full)
17.50A 17.50A 56.00A 3.00A  0.80A 933w /
848w
90.88%  50.7°C /
51.5°C
 0.9°C
3.24v 5.04v 12.14v 4.92v -11.87v
Test 5
(x-load)
17.00A 16.00A 1.00A 0.00A 0.00A  176w /
149w
84.65% 52.0°C /
52.8°C
0.8 °C
3.30v 5.08v 12.20v 5.09v -12.47v
Test 6
(x-load)
 1.00A  1.00A  69.40A  0.00A  0.00A  913w /
850w
93.09%  51.2°C /
52.5°C
 1.5°C
3.29v 5.06v 12.14v 5.06v -13.06v
Test 7
(MAX)
 21.00A  21.00A 73.00A  4.50A  0.60A  1206w /
1084w
89.88%  49.9°C /
52.0°C
 2.1°C
3.21v 5.02v 12.09v 4.85v -12.09v
 
Bumping up the ambient temperature to a toasty 50°C and re-running the room temperature results, hardy anything at all changed. In fact, aside from the odd +/-0.2v fluctuation on a couple of the rails and a few dips in efficiency, the results might as well be classed as identical. It really is beginning to look like nothing I can throw at the HX850W can phase it in any way, shape or form.
 
Corsair HX850W Scope Results @ 50c
   +3.3v  +5.0v  +12v
Test 1
(Low)
T1_3.3V T1_5V T1_12V
Test 2
(Med)
t2_3.3v t2_5v t2_12v
Test 3
(High)
t3_3.3v t3_5v t3_12v
Test 4
(Full)
t4_3v t4_5v t4_12v
Test 5
(x-load)
t5_3.3v t5_5v t5_12v
Test 6
(x-load)
t6_3.3v t6_5v t6_12v
Test 7
(MAX)
T7_3.3 T7_5 T7_12

For the last part of the testing I analysed the ripple on the +3.3, +5 and +12v rails using a Rigol 25Mhz 400MSa/s oscilloscope. All readings were taken while the HX850W was installed inside the 50°C hot box to provide us with worst case scenario results.
 
Yet again the HX850W gave stunning results with the +3.3v and +5v rails staying below 10mV ripple in tests 1-6 and only hitting 12mV ripple in test 7. The +12v rail was also extremely clean with ripple starting at 10mV in test 1 and only increasing to 32mV by test 4. Test 7 saw the ripple hit 42mV, but this is still way below the maximum of 120mV as specified by ATX standards.
 
Now let's move on to the conlcusion where I try to sum up everything seen today...


Corsair HX850W (850w) ATX PSU Page: 5
Conclusion
 
Corsair HX850WThey say that some things get better with age, and in the case of Corsair's HX series at least I'm inclined to agree. The HX620W was a great PSU, the HX1000W even better. But when it come to designing and building the HX850W Corsair have realy pushed the boat out and delivered something that is truly special.
 
Right from the word go the HX850w impresses. The packaging, the accessories, the immaculate powder coated finish. It all makes you feel like you've got a PSU that is just a little bit better than the rest. Then there's the flat 'ribbon cable' style modular cables. They may have made their first appearance quite some time ago, but they really do look the business inside a PC, and as you'd expect Corsair have provided enough cables to hook up everything from a triple-GPU gaming system to a storage junkies RAID array that would make even Google proud.
 
But the real star of the show is the performance. Never before on OC3D have I come across a PSU that can laugh in the face of our load testing equipment by deliverying rock solid voltages all the way up to its rated output along while also operating as cool as a cucumber and delivering insanely high levels of efficiency.
 
Even in the cross load tests that normally bring most PSU's to their knees, the HX850W continuted to operate as if nothing was happening. Furthermore, the recently introduced 'Max Load' test really showed just how powerful the HX850W is with the unit hitting 1084W before starting to show signs of strain.
 
To cut a long story short, the Corsair HX850W has raised the bar for what consumers should expect from a PSU. No longer do you have to choose between performance, efficiency, looks, price or silence. The HX850W has it all.
 
The Good
- Extremely high efficiency at around 90-93%.
- Runs so cool, it almost seems like it doesn't need a fan!
- Excellent voltage regulation on all rails, even in cross load situations.
- Ripple almost non-existant on +3.3v and +5v rails. Also very low on +12v rail.
- High quality internal components.
- Great modular connector system with plenty of sexy 'flat' style cables.
- Well packaged. Hardly any chance of damage during shipping.
- Delivers so much more than what it says on the box. 1084W to be precise!
 
The Mediocre
- Would quite like for hard-wired cables to use the same 'flat' style cables as the modular connectors.
 
The Bad
- Nothing at all
 
In recognition of the HX850W's outstanding performance Overclock3D is pleased to award the unit our highly coveted Best In Class Award in the PSU class of 850-1000W.
 
Overclock3D Best In Class Award
 
Thanks to Corsair for sending the HX850W in for review. Discuss this review in our forums.