The PSU is cooled by a 140x140x25mm fan (Yate Loon D14SH-12).
Like the above-discussed HPU-4M630, the HPU-4M880 has four “virtual” +12V lines but two of them are rated for a current of 30A rather than 18A. The graphics card cables are connected to these 30A lines. Each such cable has two connectors and should be able to power up any graphics card which may require as much as 260W, e.g. the Radeon HD 4870 X2. The combined load of the 12V rail must not be higher than 64A. So, this PSU should be enough for a system with an advanced processor and a couple of 4870 X2 cards.
The PSU worked normally at loads from 50 through 860W. Together with an APC SmartUPS SC 620 the power supply worked at loads up to 380W (from the mains) and 340W (from the batteries). The UPS switched to its batteries and back to the mains without problems.
The output voltage ripple fits within the permissible limits, but by a narrow margin on the +12V rail.
The output voltages are very stable. The +12V voltage keeps within a 1% deflection from the nominal value. The +5V voltage is within a 2% deflection. The +3.3V voltage deflects by 4% at an extreme load (but the permissible maximum is 5%). Thus, the 4M880 can work under any combination of loads within its specified load range.
The PSU is 87% efficient. Its power factor is 0.99. It is good that the efficiency doesn’t change much at loads of 150W through maximum.
The PSU is not noisier notwithstanding its higher wattage. The fan speed is no higher than 900rpm at loads below 450W. Then it grows up linearly up to 1600rpm. Thus, the HPU-4M880-PE is average in terms of noisiness.
Summing everything up, the HPU-4M880-PE has all the advantages of the HPU-4M630-PE model I have discussed above. It is a well-assembled, stable and quiet PSU. Its wattage and cables should suffice even for a computer with two top-end graphics cards like Radeon HD 4870 X2 or GeForce GTX 280. The number of SATA power connectors is the only thing you can gripe about. I guess a modern PSU of this class should have about six of them since hard and optical drives have already transitioned to the SATA interface.