Corsair HX1000W Power Supply Review
By Gabriel Torres on November 11, 2008
Corsair HX1000W is a 1,000 W power supply with six 6/8-pin auxiliary cables for video cards (four on the modular cabling system and two coming directly from inside the unit), modular cabling system, solid aluminum capacitors, dual-transformer design and with the manufacturer saying that it can really deliver 1,000 W at 50° C. Let’s see if this is true and if this is a good product.
As you can see in Figure 1, this power supply uses a big 140 mm ball bearing fan on its bottom and a big mesh on the rear side where traditionally we have an 80 mm fan. We like this design as it provides not only a better airflow but the power supply produces less noise, as the fan can rotate at a lower speed in order to produce the same airflow as an 80 mm fan.
Because of its internal design using two transformers instead of just one (translation: internally there are two complete and independent power supplies inside this product) Corsair HX1000W is bigger than regular power supplies, with a depth of 7 7/8” (20 cm) instead of 5 33/64” (140 mm).
This power supply has active PFC, so it can be sold in Europe, and because of that it also features auto voltage selection. Corsair says this unit has 80% minimum efficiency. Of course we will measure efficiency during our tests.
The main motherboard cable uses a 20/24-pin connector and comes inside the power supply housing. The EPS12V connector also comes from inside the power supply housing and can be separated into two ATX12V connectors. Two of the 6/8-pin auxiliary cables for video cards come from inside the power supply housing. All other cables use the modular cabling system.
This power supply comes with 13 cables to be used with its modular cabling system inside a pouch: one additional EPS12V/ATX12V cable (can’t be used if all four auxiliary power cables for video cards are being used), four 6/8-pin auxiliary power cables for video cards (all with a ferrite bead at one end to help reducing electrical noise), two cables with four SATA power connectors each, two cables with two SATA power connectors each, two cables with four peripheral power connectors and one floppy disk drive power connector each and two cables with two peripheral power connectors each.
You have to pay attention because this power supply comes with a total of eight SATA and peripheral cables, but the modular cabling system has only six connectors for them.
On this power supply all wires are 18 AWG.
Like other power supplies from Corsair with modular cabling system, the cables used on this system have their wires stuck together, which surely helps organizing the cables inside the PC for a better aesthetics and airflow. The cables coming from inside the power supply housing use a nylon sleeving, but it doesn’t come from inside the power supply housing.
It is very important to notice that HX1000W uses a completely different design from other power supplies from Corsair’s HX series. Not only HX1000W uses a dual-transformer design, but it is also manufactured by a different company, CWT. Other HX models are manufactured by Seasonic, which also manufactures power supplies from Corsair’s VX series. CWT is also in charge of Corsair’s TX series. Power supplies from Thermaltake are also manufactured by CWT and Toughpower 1,000 W and above units use the same internal design as Corsair HX1000W. In fact, internally Corsair HX1000W is identical to Thermaltake Toughpower 1,500 W – a model labeled 50% above the reviewed unit. The only difference between them is the use of multiple rail design on Thermaltake’s model. We will discuss more about this later.
Now let’s take an in-depth look inside this power supply.
We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.
This page will be an overview, and then in the following pages we will discuss in detail the quality and ratings of the components used.
What immediately got our eye was the fact that this power supply has two completely independent 500 W power supplies inside. Usually power supplies with two transformers the switching section is shared (i.e., there is only switching section that drives both transformers) or the secondary outputs are connected together. This isn’t the case with this unit. As you can see, there are even two separated active PFC circuits, one for each power supply. The only thing that is shared among them is the transient filtering stage and the rectification bridge.
The +5VSB (standby) power supply is built on a separated printed circuit board (see Figures 5 and 6).
As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils (the two coils with a black rubber protection on the pictures below), two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor, yellow component on the pictures below) and one MOV (Metal-Oxide Varistor, yellow component with black rubber protection in Figure 10). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.
The transient filtering stage from this power supply is flawless, with two extra Y capacitors, one extra X capacitor and a ferrite bead attached to the main AC cable.
As explained in the previous page, this section is shared by the two 500 W power supplies inside Corsair HX1000W.
Thermaltake Toughpower 1,500 W and Corsair HX1000W are identical on this stage.
In the next page we will have a more detailed discussion about the components used in the HX1000W.
On this page we will take an in-depth look at the primary stage of HX1000W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses two GBU1506 rectifying bridges connected in parallel in its primary, each one capable of delivering up to 15 A at 100° C (if a heatsink is used, which is the case), so the total capacity is of 30 A at 100° C. This stage is amazingly overspec'ed: at 115 V this unit would be able to pull up to 3,450 W from the power grid; assuming 80% efficiency, the bridges would allow this unit to deliver up to 2,760 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.
These bridges are shared among the two 500 W power supplies that exist inside HX1000W. But all sections from now on are really separated. As we mentioned, usually power supplies using two transformers share at least the active PFC circuit. On Corsair HX1000W everything is separated, including the active PFC circuit: separated switching transistors, separated PWM/PFC controlling circuit, separated transformers and separated outputs. So we are really talking about two independent power supplies here (well, not exactly, as they still share the rectifying bridges).
Each active PFC circuit uses two 20N60C3 power MOSFET transistors, the same used by several other power supplies we looked. Each one is capable of handling up to 300 A @ 25° C in pulse mode (which is the case) or up to 45 A @ 25° C or 20 A @ 110° C (note the difference temperature makes).
On each switching section this power supply uses two other 20N60C3 transistors, on the traditional two-transistor forward configuration. The specs for these transistors are published above.
Each primary is controlled by a CM6800 active PFC/PWM controller combo installed on a small printed circuit board.
Each active PFC stage uses one Japanese electrolytic capacitor from Chemi-Con rated at 105° C. This is outstanding.
Thermaltake Toughpower 1,500 W and Corsair HX1000W are identical on this stage.
Each secondary is completely independent, with one of them generating the +5 V and the +12V1 rails and the other generating the +3.3 V and +12V2 rails. Notice that +12V1 and +12V2 are not virtual rails like happens with power supplies with only one transformer: they are completely separated rails produced by independent power supplies.
This power supply is basically a +12 V power supply, with the +12 V output the +5 V and +3.3 V outputs being produced using DC-DC converters (i.e., a small switching power supplies) connected to the +12 V output. Each secondary uses two MBRH300EPT Schottky rectifiers, one STPS30H100CW Schottky rectifier and one STP140NF75 Power MOSFET transistor to produce the +12 V output.
The capacitors used on the secondary are all solid and here Corsair HX1000W is even better than Thermaltake Toughpower 1,500 W, because Thermaltake’s model uses solid caps only to filter the +5 V and +3.3 V outputs, using regular Japanese caps to filter the +12 V outputs. As mentioned, on Corsair HX1000W all capacitors are solid.
Each secondary is controlled by its own monitoring integrated circuit (PS229), which is installed on a small printed circuit board. Unfortunately the specs for this circuit aren’t available on the manufacturer’s website.
We were really surprised to see that Thermaltake Toughpower 1,500 W and Corsair HX1000W are also identical on this stage, especially because Thermaltake’s model is rated with a maximum power output 50% above HX1000W’s. In fact Corsair HX1000W is a little bit better, as it only uses solid caps on the secondary, while on Thermaltake Toughpower 1,500 W only the caps connected on the +5 V and +3.3 V are solid.
In Figure 19, you can see the power supply label containing all the power specs.
Each power supply inside HX1000W has a single-rail design, so this power supply has two independent +12V rails, +12V1 and +12V2. This is one of the main differences between Corsair HX1000W and Thermaltake Toughpower 1,500 W. Thermaltake’s model has four +12 V virtual rails, two for each power supply. The difference between a single rail design and a multiple rail one is how the over current protection (OCP) is connected. On single rail design there is only one OCP circuit that monitors all the +12 V outputs at the same time, while on multiple rail design the power supply has several OCP circuits, each one monitoring a group of +12 V wires (the virtual rails).
The two rails are distributed like this:
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load. Then we tried to pull even more power from this unit and the results for this test are in the next page.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
Because HX1000W has two independent power supplies inside, we had to take extra care to not pull all current/power from only of them, what would make the power supply to shut down or have an unexpected behavior. So to the +12V1 input from our load tester we connected only cables that were connected to the +12V1 rail from the power supply (motherboard main connector, EPS12V connector and video card connector from the modular cabling system). We did the same thing with the +12V2 input: we connected the video card connector that comes from inside the power supply, which is connected to the power supply +12V2 rail. So on results below +12V1 and +12V2 really represent the +12V1 and +12V2 rails from the power supply.
8 A (96 W)
14 A (168 W)
22 A (264 W)
30 A (360 W)
33 A (396 W)
8 A (96 W)
14 A (168 W)
11 A (264 W)
30 A (360 W)
33 A (396 W)
2 A (10 W)
6 A (30 W)
8 A (40 W)
10 A (50 W)
22.5 A (112.5 W)
2 A (6.6 W)
6 A (19.8 W)
8 A (26.4 W)
10 A (33 W)
22 A (72.6 W)
1 A (5 W)
2 A (10 W)
2 A (10 W)
3 A (15 W)
3.5 A (17.5 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
% Max Load
Ripple and Noise
AC Power (1)
|AC Power (2)||264.5 W||484.7 W||738.0 W||977.0 W||1,225.0 W|
|AC Voltage||109.1 V||106.3 V||103.4 V||100.1 V||96.6 V|
Updated 06/25/2009: We re-tested this power supply using our new GWInsteak GPM-8212 power meter, which is a precision instrument and provides accuracy of 0.2% and thus presenting the correct readings for AC power and efficiency (results marked as "2" on the table above; results marked as "1" were measured with our previous power meter from Brand Electronics, which isn't so precise as you can see). We also added the numbers for AC voltage during our tests, an important number as efficiency is directly proportional to AC voltage (the higher AC voltage is, the higher efficiency is). Also, manufacturers usually announce efficiency at 230 V, which usually inflates efficiency numbers. We added power factor (PF) numbers as well. These numbers measure the efficiency of the power supply active PFC circuit. This number should be as close to 1 as possible. Under light load (20% load, i.e., 200 W), the active PFC circuit from this unit isn't as good as when operating under higher loads, but 0.989 is still an excellent number. At full load power factor was of 0.999, which is probably as high as you can get!
This power supply can really deliver its labeled power at 50° C (on test number five we collected data when the temperature inside our thermal chamber was at 47° C, but we let it working after that to see what would happen and the power supply worked fine at temperatures above 50° C).
Efficiency was always above 80%, however there are other 1,000 W power supplies that present higher efficiency, like OCZ EliteXStream 1000 W.
Pulling 1,000 W +5 V and +3.3 V voltages dropped to 4.76 V and 3.18 V, respectively. These values are still inside the 5% tolerance set by the ATX specification, but we wanted to see these values closer to their nominal voltages. On the other hand, we have an explanation for this behavior.
Our load tester is limited to 33 A (396 W) for each of its +12V inputs. To achieve 1,000 W we had to pull more current from +5 V and +3.3 V outputs than we wanted (we try to pull as much as we can from the +12 V outputs, since current PCs will pull more current/power from +12 V, which is the line that feeds the CPU and the video cards). Because the peripheral and SATA power connectors were connected to the +12V2 rail, we didn’t connect them to the load tester, because on our load tester peripheral connectors are physically connected to the +12V1 input, and we didn’t want to mix +12V1 and +12V2 rails. So the wires on the main motherboard cable were the only ones carrying +5 V and +3.3 V voltages and we believe that voltage dropped because we didn’t have more wires carrying these voltages connected to the load tester.
In summary, it is our opinion that you should not worry about these values we achieved.
For all other tests voltages were within 3% from their nominal values.
Ripple and noise were below the maximum allowed: less than a half from the maximum admissible, even when we were pulling 1,000 W from the reviewed unit.
Below you can see noise level when we were pulling 980 W (test number five) from this power supply. Just to remember, the maximum allowed for the +12 V outputs is 120 mV peak-to-peak and the maximum allowed for the +5 V and +3.3 V outputs is 50 mV peak-to-peak.
Now let’s see how much power we could pull from this unit keeping it working inside ATX specs.
Before overloading the power supply we always test to see if the over current protection (OCP) circuit is active and at what level it is configured.
To do this we installed one auxiliary video card power cable from the modular cabling system to the +12V2 input from our load tester and removed the auxiliary video card power cable that was installed to the +12V1 input from our load tester. This way we had only +12V1 rail from the power supply connected to our load tester.
Under this configuration the power supply should shut down if we pulled too much current. The power supply label states a 40 A limit for each rail. We configured our load tester to pull 33 A from the motherboard main cable and EPS12V cable plus another 33 A from the auxiliary video card cable for a total of 66 A being pulled from HX1000W’s +12V1 rail, but the power supply didn’t shut down.
This means that either the over current circuit is disabled or it is configured at a value above 66 A. We couldn’t pull more than that due to a limitation of our load tester.
On the other hand the power supply worked fine under this extreme condition. Unfortunately we were limited by our equipment. Otherwise we’d like to try pulling 66 A from +12V2 at the same time to see what would happen. If the power supply survived, it would show us that we were facing a model capable of delivering at least 1,500 W on its +12V outputs, plus what it could deliver on the other outputs (+5 V, +3.3 V, +5VSB and -12 V).
With our original cable configuration (as describe in the previous page) we started increasing current to see what would happen. But this test wasn’t fair: since we had already maxed out the +12 V outputs, we could only increase current on +5 V and +3.3 V, which isn’t our preferred way of overloading a power supply because, as we explained before, we are more concerned about how much current/power the +12 V outputs can deliver.
From test number five we increased current on +5 V and +3.3 V to 30 A each. Under this configuration we were pulling 1,039 W from the power supply at 47° C. We probably could pull more from this power supply if we weren’t limited by our equipment, so we couldn’t measure the real maximum power HX1000W can deliver.
We are very confident that HX1000W is really a 1,500 W power supply – since it is internally identical to Thermaltake Toughpower 1,500 W – but Corsair decided to label it as a 1,000 W model because of efficiency: pulling more than 1,000 W efficiency will probably drop below the 80% mark and if Corsair labeled this unit as an 1,100 W unit or even an 1,200 W it couldn’t guaranteed a minimum 80% efficiency at full load and it wouldn’t be able to get the “80 Plus” certification.
HX1000W power supply specs include:
* Researched at Shopping.com on the day we published this review.
We were impressed to see that Corsair HX1000W is internally practically identical to Thermaltake Toughpower 1,500 W, a unit labeled with a maximum power capacity 50% above Corsair’s model!
There are three major differences between Corsair HX1000W and Thermaltake Toughpower 1,500 W, though. First, the modular cabling system has a different configuration. On Corsair HX1000W there are six connectors for peripheral and SATA cables, while on Toughpower 1,500 W there are only four. On the other hand, on HX1000W there are four connectors for auxiliary video card power cables, while on Toughpower 1,500 W there are six.
The second major difference is on the use of two virtual rails on each +12 V rail on Toughpower 1,500 W, feature not present on HX1000W. This means that each power supply inside HX1000W uses a single-rail design, while each power supply inside Toughpower 1,500 W uses two virtual rails, for a total of four +12 V rails. The difference between a single rail design and a multiple rail one is how the over current protection (OCP) is connected. On single rail design there is only one OCP circuit that monitors all the +12 V outputs at the same time, while on multiple rail design the power supply has several OCP circuits, each one monitoring a group of +12 V wires (the virtual rails).
And the third difference, and here Corsair HX1000W has an advantage, is that all capacitors on the secondary are solid. On Toughpower 1,500 W only the capacitors used on the +5 V and +3.3 V rails are solid.
We are pretty confident that Corsair HX1000W is in fact a 1,500 W power supply that Corsair decided to label as a 1,000 W model because of efficiency. If Corsair had labeled this unit as a 1,100 W or greater unit it wouldn’t achieve the minimum 80% efficiency at full load that is considered by today’s standards the minimum a power supply should perform.
The efficiency from this power supply is decent (between 80.0% and 83.1% depending on the load), put there are 1,000 W units around that present higher efficiency, like OCZ EliteXStream 1000 W.
The number of cables available on this unit is outstanding and will allow you to build a three-way SLI using three GeForce GTX 260 or GTX 280 directly without the need of using any kind of adapter on the power supply, as it has six video card power cables (each GTX 260 or 280 will take two cables). However if you want to install four very high-end video cards from ATI you will need to use adapters to convert peripheral power plugs into video card auxiliary power plugs for the fourth card.
The overall internal quality of this power supply is outstanding. Besides the solid aluminum caps on the secondary, it uses a Japanese cap on the active PFC circuit labeled at 105° C. Remembering that this power supply uses a dual-transformer design with independent circuits, making this power supply to have two separated power supplies inside. The only circuit that is shared among the two internal power supplies is the rectifying bridge. Usually power supplies with two-transformer design shares the active PFC and switching sections, which isn’t the case with HX1000W.
And the price of this baby is not even close to its main competitor, Thermaltake Toughpower 1,000 W – which curiously uses the exact same design of this power supply. Corsair HX1000W can be found, on average, by USD 235, while Toughpower 1,000 W costs, on average, USD 290 (prices for the US market).
In summary Corsair HX1000W is a practically flawless 1,000 W power supply clearly targeted to users with three or four very high-end video cards and several hard disk drives. Of course if you are building a more modest system with only one or two video cards, you should buy a more inexpensive product, which will give you a better cost/benefit ratio.