The high-frequency pulsations of the output voltages are about 40 millivolts, which is not low, but fits into the acceptable limits.

The management of the fan speeds is very efficient in this PSU, and the fans themselves have low speeds. I can’t but mention two additional functions of the unit. First, it has fan connectors whose voltage changes depending on the temperature inside the PSU (this voltage is listed in the third column of the table above). Second, after the computer is shut down, the fans still work at their minimal speed for three minutes, powering from the standby +5v source, to cool the system down completely. Well, the first function loses its appeal somewhat now that there are modern mainboards capable of controlling the speeds of the attached fans depending on the chipset and CPU temperatures or manually. The second function is going to elongate the life of the PSU and computer components, but its practical effect is rather small.

In spite of the large ribs of the heatsinks, the low speed of the fans told anyway: the temperature of the diode assemblages was rather high (although far from critical). Yet, I couldn’t call this unit a noiseless one, since the top fan produced a soft buzz, quite audible in a quiet room.

Of course, I didn’t wait for any miracles from the P4-450W after I had tested the True430P, but its cross-load characteristics proved to be worse even than those of many other classic-design power supplies, not mentioning PSUs with independent voltages regulation.

The diagram shows that this power supplies doesn’t keep the output voltages as stable as they should be. It doesn’t tolerate a load misbalance towards the +5v as well as the +12v power rail, although many lower-wattage units are better with the latter. Well, partially this comes as the initially high +5v voltage went too quickly out of the acceptable range when the load on the +12v grew up. But on the other hand, the power supply cannot boast a high stability, either, when there’s a high load on the +5v and a low load on the +12v.

That said, the P4-450W power supply from BeQuiet is an ambiguous product. Yes, the assembly is neat, the unit itself is quiet and has good parameters, but these parameters still don’t allow it to be called a high-power and noiseless PSU. If we were to compare the specifications, the P4-450W would appear slightly better than the above-described Antec, but it is much worse in practice as the comparison of their cross-load characteristics shows. Moreover, the average retail price of the P4-450W (about 80 euros) is considerably higher than the price of the Antec True430P and is close to the price of the 470W unit from OCZ I’m going to discuss below.