To achieve comparable values, we divided the power supplies into two output classes: 400 to 449 Watts and 450 to 520 Watts. This division is based on the output value listed by the manufacturer. In the 400- to 449-Watt class, the Zalman ZM400A-APF has excellent values and adequate reserves, while the Antec True 480P, in the 450- to 520-Watt class, receives our recommendation.

At 484 Watts, the True 480P was the power supply with the highest output in the test. Although the Zalman power supply has a maximum output of 447 Watts, the 400-Watt PC Cooling Ultra-Silent, delivering 452 Watts, is the hands-down winner. Also, the +3.3-Volt line in the Zalman ZM400A-APF sinks below the tolerance level of 3.14 V at higher outputs without the power supply powering down.

If power supplies become too hot as a result of overloading or a voltage drop, the devices should switch off automatically. This prevents the hardware from being damaged. The user also has the option of removing those components responsible for the overload. In the test, however, only Chieftec HPC-420-302 DF and the Verax ST-400 HLP correctly detected an overload and switched off.

What's really unacceptable is when the devices permanently halt operation due to overloading and then refuse to start again even following a cooling-off period.

In these cases where the causes of the overload are not apparent, the only option for the user is to buy a new power supply. Thus, the PC Cooling Ultra-Silent 400 gives up the ghost at an overload of 435 Watts. The same happens with the Seasonic SS-400FS. The 400-Watt power supply withdraws from service at an overload of 438 Watts and cannot be switched on again even after cooling off.

The Zalman ZM400A-APF alone is well documented when it comes to individual output details.