Articles: Cases/PSU

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Corsair CMPSU-1000HX (1000W)

This model has been tested twice in our labs. First time the PSU had rather poor results but the problem was in the specific sample. So, I am going to show you the test results of a second sample of this PSU.

Each series of Corsair PSUs has a distinctive color. Blue is the color of the CMPSU-1000HX, so you will distinguish its box among others easily. I wish the box had a handle and could be carried about that easily, too.

Exterior Design

The PSU has a large (200mm long) housing painted matte black. There are no decorations, making the CMPSU-1000HX look restrained and demure.

Most of the PSU’s cables are detachable. There are Molex Mini-Fit Jr. connectors for them at the back panel. The connectors for graphics card and peripheral cables differ in size and color, so you can’t plug them wrong.

The cables are designed in an original way. They are flat, black and lack any color marking for different voltages and signals. Adjacent wires are joined together along the entire cable, so the cable is neater and more flexible than in the classic variant when a few individual wires are contained within a meshed nylon sleeve.

There are ferrite rings at the ends of the graphics card cables. They acts as high-frequency noise filters.

The PSU is equipped with the following cables and connectors:

  • Mainboard cable with a 20-4-pin connector (60cm)
  • CPU cable with a 4+4-pin connector (63cm)
  • Two graphics card cables with one 6+2-pin connector on each (61cm)
  • Four connectors for additional graphics card and CPU cables
  • Six connectors for peripheral power cables

Included with the PSU are:

  • Four graphics card cables with one 6+2-pin connector one each, with ferrite rings (61cm)
  • CPU cable with a 4+4-pin connector (60cm)
  • Two cables with four Molex connectors and one floppy-drive plug on each (45+10+10+10+10cm)
  • Two cables with two Molex connectors on each (40+10cm)
  • Two cables with four SATA power plugs on each (45+10+10+10cm)
  • Two cables with two SATA power plugs on each (40+10cm)

So, there is everything you might want from a modern PSU. This model allows connecting three top-end graphics cards and a large RAID array without any adapters. As you can see there are more peripheral power cables in the kit than there are connectors in the PSU. It means the user can choose what power connectors are necessary for his particular computer. The short cable with two Molex connectors is handy as it is going to be enough for most systems (if you want such connectors at all). The CPU and graphics card cables are long enough for this price category while the HDD cables are rather too short. Their flexibility makes up for the shortness, though.

Interior Design

The CMPSU-1000HX can be instantly recognized as the monstrous “two power supplies in one housing” design developed and manufactured by Channel Well. I provided a detailed description of such PSUs, which sell under different brands, in an earlier review. Briefly, there are indeed two virtually independent 500W power supplies inside the CMPSU-1000HX, one providing +12V and +3.3V and the other +12V and +5V. Each PSU has a dedicated high-voltage section, starting from active PFC.

CWT engineers developed this design in order to release PSUs with wattage ratings up to 1500W and with more or less ATX-like dimensions. However, they are going to leave the scene soon as they are too complex. CWT has already developed a 1200W PSU with traditional design. It was discussed in our review of Ikonik power supplies.

The PSU makes use of independent step-down regulators to get +5V and +3.3V voltages out of +12V. The main power transformers only generate the latter voltage, which makes them smaller and somewhat cheaper to manufacture.

A small card of the +5V standby source hangs next to the external vent grid. This position improves the cooling of the standby source (and it becomes hot when the main part of the PSU and its fan are turned off, so the proximity of cold outside air is very good for it), but produces additional resistance to the air flow in the already cramped PSU.


The distinguishing feature of PSUs based on this design is that the output power rails are all divided into two groups, and the combined load in each group cannot be higher than 500 watts. Thus, you can only squeeze the full 1000 watts out of this PSU if your load is ideally split into two 500W groups. Therefore, the effective output power of this PSU may differ greatly from its specification.

On the other hand, this separation ensures higher stability of the output voltages because any surges of voltage in one group cannot affect the output voltages of the other group.

Otherwise, the specifications are standard enough for this product class.

UPS Compatibility

Together with my APC SmartUPS SC 620 this power supply worked at loads up to 380W when powered by the mains. The pair was not particularly stable on the batteries. They switched to the batteries normally but then the UPS would produce characteristic gurgling sounds and shut down in half a minute, reporting overload, even at a load of only 300W.

Thus, an UPS with sinusoidal output voltage is recommended for this power supply.

Output Voltage Stability

The +12V voltage (I measured the output voltage of one of the sub-PSUs, the total load being equally distributed between them) boasts excellent stability. It does not deflect more than 1% from the nominal value. The +5V and +3.3V voltages reach a 4% deflection but do not violate the limits even at high loads.

Output Voltage Ripple

At the maximum permissible load the high-frequency ripple on the +12V rail is very low. On the +3.3V rail it is as high as the allowable limit, but that’s not a problem really.

The low-frequency pulsation is barely visible.


The PSU is cooled with a 7-blade 140x140x25mm fan from Yate Loon.

The fan speed is below 1000rpm at loads up to 350W and the PSU is rather quiet then. When the fan accelerates at higher loads, the speed goes up to 2000rpm, making the CMPSU-1000HX a rather noisy thing. This PSU is only comfortable for your ears at loads below 450W.

Efficiency and Power Factor

The PSU is 85% efficient at the maximum but its efficiency declines at higher loads, being barely above 80% at 970W. The power factor varies much depending on load, which is rather odd.


The Corsair CMPSU-1000HX is undoubtedly a high-quality product. However, it has a number of stronger opponents that are superior in one or another parameter. On the downside of this model are its very large dimensions, noisy fan (even at medium loads) and a very complex (and thus potentially less reliable) circuit design.

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