5-way High-End 1KW+ PSU Round-Up Page: 1
1KW+ PSU RoundupPCP&C TurboCool, Enermax Galaxy and the Tagan TurboJet. These were some of the very first 1KW+ power supplies to hit the end user market over two years ago. Since then every manufacturer and his dog has wanted to get a piece of the 1000w action, with many companies such as BFG and Gigabyte who have had no previous experience in PSU manufacture joining the fray. Now two years down the line, the market is simply overwhelmed. Just taking a look at popular retailers websites, we can see models from Akasa, Zalman, OCZ and Tuniq to name but a few.
But which of these manufacturers should you choose when specing up your new PC system? As we've shown in the past, all 1KW units certainly aren't made equal and some of the most unsuspecting manufacturers can sometimes surprise you. Today we're going to be taking a look at a handful of the latest PSU's:- some from veteran manufacturers, some from new kids on the block to see exactly what they are made of. Below is the lucky list of contenders:
Be-Quiet Dark Power Pro 1200w
Cooler Master UCP 1100w
Corsair HX1000 1000w
• Enermax Revolution 1050w (Pre-Release)
Silverstone Zeus 1200w
Let's start by checking out our first subject over on the next page...

5-way High-End 1KW+ PSU Round-Up Page: 2
Be-Quiet Dark Power Pro 1200w
First up under the spotlight (which we'll shine in alphabetical order just to be fair) is the Dark Power Pro 1200w. We first got introduced to the Dark Power series a short while ago when Be-Quiet asked us to take a look at their rather sexy, yet slightly expensive 650w model.
Be-Quiet 1200w Specs 
be-Quiet Dark Power Pro 1200w Box Be-Quiet Dark Power Pro 1200w Box
Be-Quiet Dark Power Pro 1200w Box Be-Quiet Dark Power Pro Box
The Dark Power Pro 1200w features exactly the same packaging design as its little brother, with a fairly minimalistic front complete with a flap that can be opened to reveal the PSU's 120mm fan area sitting behind a plastic window. Modular cables are spread out over three seperate compartments with a final fourth compartment for the mains cable, screws and cable ties.
Be-Quiet Dark Power Pro 1200w Side Be-Quiet Dark Power Pro 1200w back
Be-Quiet Dark Power Pro 1200w Top Be-Quiet Dark Power Pro 1200w Front
Measuring in at 180mm long, the Dark Power Pro is not only the PSU with the highest output rating, but it's also one of the shortest. Coming complete with a highly reflective electroplated finish, gold plated fan grill and colour coded modular plugs, some may also say that it's one of the most visually appealing too.
Those of us with a keen eye will also notice that Be-Quiet have made a departure from the normal kettle lead style plug, in favour of the new European style. This is significantly larger than its predecessor and looks much more capable of handling the 1200w+ that this unit will be drawing from the mains during our testing.
Be-Quiet Dark Power Pro 1200w Modular Be-Quiet Dark Power Pro 1200w Cables
The modular connector system on the Dark Power features a total of 11 connectors (not including the four fan headers) with a combination of PCI-E and flat 5-Pin style plugs being used for an extremely robust connection. Additionally, each of the PCI-E style sockets is also colour coded to prevent any of the cables finding their way into the wrong sockets and potentially damaging your precious hardware.
Dark Power Pro 1200w Plugs Dark Power Pro 1200w PCI-E
Hard-wired into the unit are a total of two cables. Normally we'd expect these to be the 24-Pin ATX and EPS12v connectors, however Be-Quiet have decided to substitute the EPS12v connector with what they call a "PHYSX PCIe Card Connector". This may sound strange considering probably only 1% of all enthusiasts own a PHYSX card, but we're happy to report that this cable can be used as an ordinary 6-Pin PCI-E VGA cable without any issues.
Be-Quiet Dark Power Pro 1200w Inside Be-Quiet Dark Power Pro 1200w Inside
Getting under the hood of the Dark Power Pro we can see that the size of the casing has taken its toll on the inside of the unit with everything being quite cramped up. However, despite this, Be-Quiet have still managed to keep all cable routing quite tidy and overall airflow through the unit should be pretty good.
Be-Quiet Dark Power Pro 1200w Transformer Be-Quiet Dark Power Pro Transformer
Positioned middle-left of the unit is the primary transformer (yellow) responsible for powering each of the six +12v rails. This is accompanied by a smaller transformer over to the right, which will more than likely deal with the +3.3 and +5v rails along with any other requirements of the ATX spec. A single 320uF, 400v capacitor manufactured by CapXon with a max operating temperature of 85c can also be seen at the lower left of the unit.
It's quite surprising that such a small amount of components can generate a stable 1.2KW of power, but we'll certainly find out for sure when we get the Be-Quiet on the load tester.

5-way High-End 1KW+ PSU Round-Up Page: 3
Cooler Master UCP 1100W
Back in 2007 Cooler Master's high-end Real Power 1000w modular PSU managed to blow our socks off with extremely good performance, efficiency and low noise levels. So much so that the PSU was actually awarded "Editors Choice" with an almost perfect 10/9/10 final score. Of course, Cooler Master's product line never stands still, and today we've been given the chance to test our their latest monster; the UCP (Ultimate Circuit Protection) 1100w.
While we cant go in to as much detail as we'd like to in the single page available in this review, Cooler Master have focused not only on the usual performance, efficiency and noise levels areas, but also on safety and MTBF. During a recent sit-down chat with Cooler Master they told us that what makes the UCP so unique is that the unit actually has a soft-on switch that powers the unit on a few seconds after the actual power switch is flipped. This prevents potentially harmful issues such as power surges and arcing, increasing the lifetime of the unit.
In fact, Cooler Master are so confident about the build quality of the unit that in most countries it actually comes with a lifetime warranty.
Cooler Master UCP 1100w Specs
Cooler Master UCP 1100w Cooler Master UCP 1100w
Cooler Master UCP 1100w Box Inside Cooler Master UCP 1100w Box Open
Being Cooler Master's new flagship PSU, the unit has certainly got all of the attention you would expect in the packaging department. While the front of the box may be rather plain with just a picture of the unit and the model number, the inside of the box is padded out with 1" thick moulded styrofoam to keep it safe from even the most careless of couriers.
Included inside are just the bare essentials: the PSU, some screws, a power cable and CD containing the manual. Maybe not quite as impressive as the keyrings and bottle openers found in some of their other PSU's, but seriously - if I wanted a bottle opener, I'd buy one from Tesco's.
Cooler Master UCP 1100w side Cooler Master UCP 1100w Back
Cooler Master UCP 1100W Top Cooler Master UCP 1100w Front
If forced to sum up the look of the UCP 1100w in one word, it would definitely be: rugged. With an extremely tough, yet almost metallic powder coated finish, the UCP is the Crocodile Dundee of the PSU world and feels like it could easily take a few bites from a large toothed 'gator without showing any signs of damage.
At the back of the unit is the usual honeycomb style grill that has become commonplace among PSU's that use anything larger than an 80mm fan. Inset into the grill is a status LED that is illuminated green under normal operation, but turns to red when the PSU detects a fault.
Unlike most of the PSU's on test here today, the UCP 1100w features a fairly small rocker-style on/off switch. However, what we need to remember here is that unlike most PSU's this switch acts only as a trigger for the delayed power-on feature, rather than an actual breaker for the full 240v that will be entering the unit.
Cooler Master UCP 1100W Bottom Cooler Master UCP 1100w Fan Grill
In terms of fan size, Cooler Master have taken a step backwards from the 135mm fans used on most of their Real Power series in favour of a 120mm version. This isn't necessarily a bad thing, as certain 120mm fans can be as quiet as their 135mm counterparts and on PSU's where the internal components don't need edge-to-edge cooling, a 120mm fan is more than sufficient.
Cooler Master haven't spoilt the looks of the unit by sticking a tacky wire-based fan grill on it either. As we can see from above, the fan grill is actually an integral part of the casing with the fan being held in place by some tasty anodised hex head screws.
Cooler Master UCP 1100w Cables Cooler Master UCP 1100w Cables
Cooler Master UCP 1100w P4-12V Cooler Master UCP 1100w PCI-E
Being the only non-modular PSU on test today, the UCP 1100w comes complete with a huge bundle of cables all neatly held together with a cable tie. Separating the bundle quickly reveals that the unit is most definitely suited to multi-GPU configurations with a total of six PCI-E cables carrying a grand total of nine PCI-E connectors. SATA and Molex devices are equally as well catered for with a total of nine and six connectors respectively.
One thing we did find slightly annoying with the cables was the quality of the sleeving. While only a cosmetic niggle, the mesh chosen by Cooler Master was extremely saggy and seemed several sizes too large for the cables. This meant under most circumstances the wires could easily be seen beneath the sleeving, partially voiding its purpose.
Cooler Master UCP 1100w Inside Cooler Master UCP 1100W Inside
Cooler Master UCP 1100w Inside Cooler Master UCP 1100w Caps
Moving on to the internals, it's instantly apparent that the UCP 1100w is much more spacious inside than the Be-Quiet Dark Power Pro over the previous page. Yet again a single large transformer caters for the step-down from the input voltage down to +12v, with a smaller transformer (situated on its own daughterboard) dealing with the further step-down from 12v down to the other voltages such as 3.3v and 5v.
Impressively the UCP 1100w has a total of three Japanese made capacitors rated at 330uF / 400v which should help smooth out out voltage fluctuations and provide clean power to the components inside your PC system.

5-way High-End 1KW+ PSU Round-Up Page: 4
Corsair HX 1000W
Corsair is a name that many enthusiasts will recognise as being one of the most respected memory manufacturers' in the industry. In 2006 they made their first entry into the PSU market with the HX620. Based on internals by Seasonic with some customisation by Corsair, the HX620 was a massive hit, winning awards worldwide. In fact, the HX620 was such a success that to this day it is one of the most recommended mid-range PSU's on the market.
Based on this success Corsair were obviously quite keen to make an equally good impression on the high-end market. However, with such a high standard being set for their HX620 the pressure was on not to disappoint power hungry Quad-SLI and CrossfireX enthusiast community. With this in mind Corsair made a switch from Seasonic as their OEM, over to CWT (Channel Well Technology) who are responsible for making some of the best PSU's in the industry.
Using CWT's 1200w Power Plus unit as the base for their new PSU, Corsair not only understated the power output of their new HX PSU by simply labelling it as "1000w", but also improved on the existing CWT components by specifying higher quality capacitors along with several other smaller upgrades and tweaks. This all certainly sounds impressive, but we'll see just how much of a difference it's made over on the testing page.
Corsair HX1000 Specs
Corsair HX 1000W Box Front Corsair HX 1000W Box Back
Corsair HX 1000W Box Open Corsair HX 1000W Contents
The HX1000 comes in a rather long double walled cardboard box that actually got us quite worried as to just how long the PSU would be once we'd unpackaged it. Thankfully on opening the box our fears were alleviated by a large quantity of Styrofoam padding along with a collection of cables and accessories neatly tucked at the end of the box.
Corsair HX 1000W Bottom Corsair HX 1000W Top
Corsair HX 1000W Back Corsair HX 1000W Side
Out of the PSU's we've covered so far in this review, the HX1000w is definitely the most professional looking of the bunch.  With a matt black, slightly coarse powdercoated finish along with blue specification stickers, there's something about the HX1000W that makes it stand out for wanting to do exactly the opposite.
Corsair have made full use of all available space and have opted for a 135mm fan. As with all PSU's of this design, the air is drawn up from inside the PC case, pushed over the heatsinks inside the PSU and allowed to exit out the back of the unit via a meshed grill.
Also worthy of a mention is the absolutely huge power switch used on the unit. While most manufacturers' tend to skimp and save, using rocker switches that look like they were stolen from a school electronics project. The switch used on the HX1000 looks more than capable of dealing with the extremely high current that this unit will be pulling from the wall socket under heavy load.
Corsair HX 1000W Front Corsair HX 1000W Modular Plugs
Corsair have kept the modular connector system extremely simple: PCI-E cables go in the blue sockets, everything else goes in the black ones. In addition, a small sticker detailing which of the two +12v rails each of the sockets is connected to internally; makes the decision of where to insert the modular plugs even easier.
Corsair HX 1000W Cables Corsair HX 1000W PCI-E
Corsair HX 1000W Wires Corsair HX 1000W ATX
The collection of modular cables is plentiful, and certainly far more than you could plug into the unit all at the same time. However, what really sets the HX1000's cables apart from those used on the rest of the modular units in this review is the total lack of sleeving.
Rather than opting for the cumbersome and often untidy look of fabric mesh finished off with heatshrink and cable ties, Corsair have decided to use black wires arranged in a ribbon cable style. This not only makes routing of the cables around the inside of the PC much easier, but also looks extremely cool.
Unfortunately the ATX, P4-12v and EPS12v cables hard wired into the unit don't follow the clean look of the modular cables and are sleeved in much the same way as the rest of the units on review. We can only assume that this is because the sleeveless modular cables are something that are added by Corsair after the unit has left the CWT factory.
Corsair HX 1000W Inside Corsair HX 1000W Dual Caps + Transformers
Corsair HX 1000W Modular Corsair HX 1000W Power Filter
Looking inside the HX1000, the layout of the internal components is so distinctive that it is instantly recognisable as coming from the same OEM that Thermaltake also use for their 1.5kw Toughpower series. However, if we compare the Toughpower unit side-by-side with the HX1000 it is clear to see that Corsair have not only upgraded the capacitors, but also changed over the transformers, upgraded the cooling and made several slight alterations to the layout as well.
What makes the unit so unique is that it is essentially two 500w PSU's placed side-by-side. This means that each of the two  +12v rails in the unit is powered by a totally independent circuit, offering unmatched stability. Not only this, but Corsair have also assigned one of the circuits to power the +5v rail, and another to power the +3.3v rail, once again offering much greater stability than any single circuit power supply could provide.

5-way High-End 1KW+ PSU Round-Up Page: 5
Enermax Revolution 85+ 1050W
With their award winning Galaxy 1KW PSU, Enermax have long been the big daddy of the high-end PSU market. So when we contacted them about conducting this review, it came as quite a shock to us that they wanted to offer us something other than the Galaxy to test. However, time stands still for no man (or PSU), and with the Galaxy having served a full two years as Enermax's flagship product it was time to bring something new to the market. Bring forth the Revolution.
The Revolution 85+ is, at time of writing,  in the final stages of pre-production; meaning that a lot of the smaller details such as packaging, accessories and manuals were not provided with the sample unit that we received. However, despite the lack of gumph that often allows us to identify some of the main features of a product, Enermax were quick to tell us that they had been concentrating hard on pleasing environmentalists this time around, and have actually developed one of the first PSU's to break 90% efficiency. Impressive!
Enermax Revolution 1050w Specs
Enermax Revolution 1050w Bottom Enermax Revolution 1050w Side
Enermax Revolution 1050w Rear Enermax Revolution 1050w Modular
Measuring in at 190mm in length the Revolution is significantly shorter than it's 220mm elder brother, making the unit much more suitable for the 'standard' sized PC case. Most of this space saving is undoubtedly down to the removal of the 80mm fan at the rear of the PSU which is no longer required due to the increased efficiency and lower heat output of the components.
In much the same style as the Be-Quiet unit seen over on page #2, the modular connector system of the Revolution uses both PCI-E style connectors as well as a flat 5-Pin style connector. Previous experience has told us that both of these systems work well, providing extremely robust connections than don't work their way loose or cause arcing due to ill-fitting plugs.
At the back of the unit you'll find the usual honeycomb grill along with the mains lead socket, a beefy power switch and a status LED. At this point it is also worth mentioning that Enermax have gotten rid of the annoying buzzer that was present on the early versions of their Galaxy and Infinity series. Having owned both of these units, the lack of 'beeping' when switching the unit on/off is a welcome ommision.
Enermax Revolution 1050w Cables Enermax Revolution 1050w Cables
Enermax Revolution 1050w Cables Enermax Revolution 1050w ATX
While we need to remember that the we're not looking at the retail version of the Revolution, the two large bundles of cables sent to us with the unit certainly look promising for those of us who have problems getting the PSU leads to reach certain parts of their full-tower cases. Furthermore, the unit is most definitely well suited to multi-GPU setups with a total of eight PCI-E connectors being provided via four modular cables.
Of course no Enermax unit would be complete without its trademark gold and black sleeved cables, and as we can see from above, the Revolution certainly doesn't disappoint. Unfortunately in some places where there are too many cables coming out of a single socket, Enermax have had to start the sleeving up to 10cm down the cable making things look a little untidy - but this is only a minor gripe.
Enermax Revolution 1050w Inside Enermax Revolution 1050w Ferrite Coil
Enermax Revolution 1050w Transformers Enermax Revolution 1050w Filter
Lifting the hood on the Revolution reveals a very tidy internal layout with minimal cable clutter and plenty of room for air to flow over and around the internals. This is surprising considering the Revolution actually has the largest number of primary components out of any of the units we've tested in this roundup.
Two beefy transformers located in the middle of the unit provide the power for the six +12v rails with a smaller transformer located just to their right dealing with all other rails such as +3.3v and +5v. Smoothing out the power are three medium sized capacitors rated at 400v / 220uF along with an AC filter fitted to the mains socket for filtering out voltage spikes and line noise.

5-way High-End 1KW+ PSU Round-Up Page: 6
Silverstone Zeus 1200w
The Silverstone Zeus range of PSU's is certainly one that we've had plenty of prior experience with here at Overclock3D. Having reviewed almost every one of their units ranging from 560w up to 1kw, the Zeus has never disappointed in the stability department mainly thanks to its server-class components. However, the Zeus series has been around for quite some time now and despite the output figures now being ramped up to 1200w, it's going to take more than rock solid voltages for this greek god to score any major points in today's tests.
Silverstone Zeus 1200w Specs
Silverstone Zeus 1200w Box front Silverstone Zeus 1200w Box Back
Silverstone Zeus 1200w Box Open Silverstone Zeus 1200w Contents
Presented in a black double walled cardboard box, the Zeus 1200w follows the same packaging style as all of its predecessors. At the front of the box we can see that Silverstone have printed a feature list along with some reassuring stickers that state that the unit can be used to power triple-GPU configurations including NVIDIA's power hungry GTX280 series. Around the back is an image of the innards of the Zeus along with fairly detailed information about each component.
Disappointingly Silverstone have placed the Zeus loose inside the box. Unlike most of the other PSU's in this round-up that use some form of Styrofoam padding inside the box to prevent the PSU from moving around and protect it from damage, the Zeus is only protected by a collection of accessories and cables all wedged inside the box.
Silverstone Zeus 1200w Top Silverstone Zeus 1200w Side
Silverstone Zeus 1200W Rear Silverstone Zeus 1200w Front
Measuring 215mm in length, the Zeus is actually the longest of all the PSU's in this test by around 10mm. This unfortunately isn't helped by the fully modular connector system which adds a further 30mm+ to the PSU's length making it only suitable for the most spacious of PC cases.
In terms of appearance, the Zeus is the most plain of the bunch with a matt black finish adorn with specification stickers on most sides. However, due to the use of an 80mm fan at the rear of the unit and a modular connector system at the front, Silverstone have been forced to add ventilation holes to the top and sides of the casing, giving the PSU a rather hardcore look.
 Silverstone Zeus 1200w Modular Silverstone Zeus 1200w ATX
Silverstone Zeus 1200w PCI-E Silverstone Zeus 1200w Modular
Taking a closer look at the modular connector system we can see that Silverstone have opted for PCI-E style plugs for all of the PSU-side connections. This is a vast improvement on the Molex style plugs used for some of the connectors on the Strider series; and should provide trouble free operation.
As required by most Tri-SLI configurations, the Zeus is equipped with a total of six PCI-E connectors. Rather than placing these on six separate modular cables, Silverstone have adopted a cable-clutter saving idea of piggy-backing two of the plugs off existing cables to reduce the total cable count to four.
Silverstone Zeus 1200w Inside Silverstone Zeus 1200w Exploded
Silverstone Zeus 1200w PCB Silverstone Zeus 1200w Filter
Just when we thought that the internal layout of the Corsair HX1000 unit would be as crazy as things could get, the Zeus comes and surprises us with a dual-PCB layout. As we can see from the images above, the Zeus is comprised of two fully loaded circuit boards separated by four large PC motherboard style spacers and a large black plastic sheet to prevent anything on either of the PCB's accidentally shorting.
This is by far the most jam packed layout out of any of the PSU's on test today (maybe ever), and despite Silverstone's attempts to keep things tidy by using zip ties on all of the cables, the 80mm fan installed in the unit is going to have a hard time keeping everything cool.
However, despite the lack of breathing space a quick look at the components used inside the unit reveals that Silverstone haven't cut any corners. Located on the upper-PCB are two primary 105c 450v Japanese capacitors along with a series of Infinion MOSFET's attached to a rather chunky aluminium heatsink. The lower half of the unit is fitted with a single full-bridge transformer, two large copper chokes and a pair of D/D modules with aluminium heatsinks for voltage regulation on the +3.3v and +5v rails.

5-way High-End 1KW+ PSU Round-Up Page: 7
Testing Procedure

Here at Overclock3D we take our PSU testing very seriously. For those of you who have read any of our previous PSU reviews, you will know that we employ our own custom made PSU load tester capable of drawing up to 1.3KW. While this certainly sounds more than perfect for testing the PSU's under the spotlight today, we wanted to go one step further and really get some solid results in both the Efficiency and Power Factor of these units - something we've only previously been able to calculate to a reasonable level of accuracy.

With all 5 PSU's in hand we set off down to the Enermax testing facilities in Milton Keynes where we had generously been given full access to their Chroma ATE 6310-E load tester. The plan was almost perfect....that was until we found out that Enermax's testing equipment wasn't geared up to test PSU's with the newer European style power sockets (Cooler Master & Be-Quiet). However, not wanting to let the day go to waste, we set out testing the remaining three units (Enermax, Silverstone, Corsair) in the hope that the other two could be tested elsewhere.
After ringing around a few contacts we struck gold. One of our friends over in Germany had access to a rather beefy Chroma ATE 6000 setup. We promptly shipped the remaining Be-Quiet and Cooler Master units over for testing with instructions on exactly what voltage, loads and ambient temperatures to test the units with so they could at least be fairly comparable to those obtained from Enermax's facilities.
Chroma ATE Enermax Load Tester
Left: Chroma ATE 6000 - Right: Chroma 6310-E

Each of the PSU's were tested at 50%, 75% and 100% load levels with voltage, efficiency and power factor readings being taken at each stage. Notes were also taken on the amount of noise that each unit produced but no exact noise measurements could be recorded due to the high ambient noise levels at both of the testing facilities.
The following charts show the exact load placed on each of the PSU's tested at the various load percentages:
Be-Quiet Load Specs
Cooler Master Load Specs
Corsair Load Specs
Enermax Load Specs
Silverstone Load Specs
Let's move on and see how each of the units faired in the results over on the next page...

5-way High-End 1KW+ PSU Round-Up Page: 8
Test Results - Voltages
When examining the performance of a PSU under load it is often all too easy to get tied up in the output voltages rather than  how stable the unit actually is. For example: PSU 'A' might have an idle voltage reading of 12.2v and a load reading of 11.9v whereas PSU 'B' might output 12.0v at idle and 11.8v under load. Common sense would tell us to opt for PSU 'A' as under load it outputs the voltage closest to our ideal +12.0v. However, while this is most certainly carries some weight. PSU 'B' actually exhibited less fluctuation between idle and load voltages, indicating that it is better equipped at coping with the stress of a heavy load.
For this reason, when viewing the graphs below we will not only be assessing the how close the voltages are to +12.0v under load, but also how flat the line is between 50% and 100% load depicting the stability of the unit.
Starting off with the +3.3v rail both the Cooler Master and Corsair units manage the least fluctuation between 50% and 100% load voltages. However, for some reason the Corsair unit seems to have its +3.3v rail voltages set a lot lower than the rest of the units in the test, with voltages as low as 3.2v being produced under full load.
The Be-Quiet and Silverstone units show the greatest dip in 50% and 100% load voltages, indicating that their +3.3v rails aren't quite as strong as the rest of the PSU's in this test.
Moving on to the +5v rail we can see that most of the results run in an almost parallel downward fashion. However, the Enermax unit doesn't seem to take kindly to the increase in load from 75% to 100% with the voltage dipping from 4.96v to 4.89v. Of course, this is still well within specification, but its certainly not as strong as the other units.
In the +12v1 and +12v2 results the most stable units are the Enermax and Silverstone, with both exhibiting little change in voltages from 50% load to 100% load. The unit with the largest visible fluctuation between light and heavy load is Corsair unit, which produced a flat line between 50% to 75% loads and then takes a rather sharp downward slope once 100% load is applied.
At the bottom of the chart is the Be-Quiet unit, which starts at a fairly reasonable 11.9v under 50% load, but then takes a fairly large drop down to 11.77v which would probably send the overclockers among us running for the hills.
On to the +12v3 and +12v4 rails and we are dwindled down to four contestants. Once again the Be-Quiet unit is sitting at the bottom of the pack with voltages as low as 11.68v under 100% load, while at the other end of the scale, the Cooler Master and Enermax exhibit the least voltage fluctuation overall.
Despite the fact that both the Enermax and the Silverstone unit are spec'ed as having six (albeit virtual) +12v rails, Enermax's Chroma 6310 only allowed for testing on four of these rails. However, both the Be-Quiet and Cooler Master units that were sent to Germany for testing on a Chroma 6000 had loads applied to each of their six rails.
As we can see from above, the Cooler Master unit produced the more stable voltages of the two units with a slightly straighter line between 50%, 75% and 100% loads. Once again the voltage output of the Be-Quiet unit under 100% load was very low, coming in 0.20v below the Cooler Master.
While not as important as the primary +3.3v, +5v and +12v rails in a PSU, the+5vsb rail is responsible for providing power to components such as USB Input Devices and Network cards while the PC is in standby mode. PSU's failing to provide enough voltage to this rail could prevent devices such as USB keyboards from functioning and allowing the system to be resumed from standby with a keypress.
As we can see from the chart above, the Corsair and Silverstone units provide the most stable voltages here between 50% and 100% load levels, with other units experiencing slight fluctuations (exaggerated by the graphs scale), but certainly nothing to worry about.
Negative voltage rails such as the -12v and -5v rails were introduced back on the original IBM PC standard PSU's and have decreased in terms of viable usage over the years. As a result the -5v rail was recently dropped from the latest PSU's when  the ATX 2.01 standard was introduced. However -12v remains, and despite its questionable usefulness the above graph shows how each PSU performed when a small load was applied to this rail.

5-way High-End 1KW+ PSU Round-Up Page: 9
Test Results - Efficiency & PFC
While voltage stability and output certainly carries a lot of weight for the consumer considering the purchase of a new PSU, Efficiency (which is quite often directly related to the noise and heat output of a unit) should also be taken into account. In general terms, efficiency is a measure of how much power was lost during the conversion between AC and DC voltages inside the PSU. The higher the efficiency percentage, the less power was lost; resulting in energy savings and often a cooler running PSU.
As mentioned earlier in the review, Enermax were keen to tell us about the work they'd put into ensuring that their Revolution 85+ PSU was one of the most efficient on the market, and this has certainly paid off. Sitting unchallenged at the top of the efficiency graph with results nearing almost 90%, Enermax have certainly got this one in the bag.
Both Cooler Master and Corsair sit roughly in the middle of the results with efficiency averaging between 84-87%, while the Be-Quiet unit has a fairly mediocre starting at 83% efficiency while under medium load, but quickly increases this 85% once additional load is applied.
Sitting at the bottom of the graph is the Silverstone Zeus which manages 82% efficiency at 50% and 75% load levels, but dips down to just under 81% efficiency at 100% load.
Interestingly the underdog in most of the previous results is the clear winner when it comes to PFC. Managing between 0.98 and 0.99 throughout the testing, the Silverstone Zeus clearly has the most advanced Active PFC circuitry of all the PSU's on test. This is more than likely down to the Zeus's enterprise server background, where organisations with large datacentres are often charged by electricity suppliers for not only their power consumption but also for their overall Power-Factor.
However, not far at all behind the Silverstone is the Enermax. Managing a 0.96 PF at 50% load, this quickly rises to 0.98 at 75% and 100% loads. The Be-Quiet unit also joins the Enermax at 50% and 100% load levels, but interestingly dips to 0.95 at 75% load.
As already mentioned back on the testing procedure page, the ambient noise levels at both of the test facilities prevented us from obtaining any useful dBA measurements from the units. However, during the testing each of the PSU's were given a score from 1 to 5 (5 being the loudest) based on personal experience.

5-way High-End 1KW+ PSU Round-Up Page: 10
Looking at the results over the previous two pages combined with the appearance and features of each of the PSU's, it's hard to single out one overall winner. Both the Silverstone, Enermax and Cooler Master units provide very stable voltages on the +12v rails with the Corsair unit also showing rock solid voltage up to 75% load, and only dipping slightly once 100% load is applied. Results on the +5v rail are very good for all units with the lowest voltage (4.89v) coming from the Enermax Revolution at 100% load.
The +3.3v rail results show a bit of separation between the units with the Corsair HX1000 having the lowest output voltages of 3.2v at full load, but also having the least fluctuation of 0.3v between 50% and 100% load levels. Units providing the best combination of voltage and stability on the +3.3v rail are Cooler Master's UCP and Enermax's Revolution, both of which not only have substantially higher output voltages than the Corsair, but also came within a whisker of its fluctuation results.
When it comes to efficiency the Enermax Revolution is the clear winner with levels approaching 90%. As expected, this also has the side-effect of making the Revolution one of the quietest and coolest running PSU's in the group with the least amount of energy being transformed into heat. Cooler Master and Corsair are also worthy of a mention here with their 135mm fans and almost-as-impressive efficiency levels resulting in cool running, reasonably quiet operation under heavy load.
While we've only touched on the actual features of each unit in today's review, the Cooler Master, Enermax, Silverstone and Corsair units need to be commended for their full support of triple-GPU systems. In addition to this, certain aesthetic features of each PSU, such as the rugged finish of the Cooler Master UCP, the excellent modular cables on the Corsair and the compact size of the Be-Quiet are all things that will appeal to enthusiasts depending on the intended use of the PSU.
The awards, final score and pro's and con's of each PSU can be seen below, but while some manufacturers will be going home empty handed, there are no real losers in this round-up. Each PSU has its own merits, and while some couldn't quite keep up with the stability and voltage output of the rest, no unit failed to provide its rated wattage output.
Be-Quiet Dark Power Pro 1200w - £173.89 from After Hours
The Good
• Compact size makes it a good candidate for smaller PC Cases.
• Easy to use, colour coded modular system with high quality cables.
• Good looks.
The Mediocre
Lack of PCI-E connectors for triple-GPU configurations. *
• Average efficiency for the group. Between 83-84%.
• Not the quietest of the bunch despite its name.
The Bad
• Low performance on the +12v rails.
* UPDATE 06/10/08 - Be-Quiet have informed us that an adapter cable should have been included in the box which provides the ability to run triple-GPU configurations with six PCI-E connectors.
Cooler Master UCP 1100w - £179.98 from Ebuyer

The Good
• Fairly quiet under heavy load.
• High efficiency levels around 86-87%.
• Extremely rugged finish and tough looks.
• Good all-round voltages and stability.
• Features such as soft-on and a 5yr warranty.

The Mediocre
• Fairly expensive.
• Cable sleeving quite slack and spoils the units look.

The Bad
• Nothing to report.

Overclock3D Recommended Award
Corsair HX1000 1000w - £146.99 from Ebuyer

The Good
• Silent and cool operation.
• Amazing value for money.
• Extremely nice and easy to route modular cables.
• Support for triple-GPU configurations with 6x PCI-E connectors.

The Mediocre
• +3.3v rail voltages run a little low.
• Very stable +12v rails up to 75% load, but slight droop thereafter.
• Good efficiency of 84-86%.

The Bad
• Nothing to Report

Overclock3D Value For Money Award
Enermax Revolution 1050w - £TBA

The Good
• Unmatchable efficiency at almost 90%.
• Very cool and quiet operation.
• Stable +3.3 and +12v rails.
• Support for triple-GPU configurations with only four cables.

The Mediocre
• +5v not quite as stable as other units, but nothing to worry about.
• Bit of an ugly ducking in its current form, but Enermax have already corrected this (1,2).
• No official price as yet.
• Only a pre-production unit. Things may change on the retail product.

The Bad
• Nothing to report.

Overclock3D Editors Choice Award
Silverstone Zeus ZM1200M - $399.99 from Newegg

The Good
• Good overall voltage stability on all rails.
• Manages a 0.98-0.99 power factor.
• Support for triple-GPU configurations.

The Mediocre
• Pretty poor efficiency compared to the rest of the group.

The Bad

• Noisy and hot under full load.
• Longest PSU in the group makes it not suitable for smaller cases.

Thanks to Be-Quiet, Cooler Master, Corsair, Enermax and Silverstone for making this review possible.
Discuss this review in our forums.