Output Voltage Ripple
If the PSU’s output voltage ripple is high, you computer may get unstable.
The junior model has no problems in this test. The output voltage ripple is within the norm (marked to the right of the diagram) on every of the three tracked power rails.
The diagram doesn’t change much for the 450W model except that the shape of pulsation is more conspicuous now on the +5V rail.
The 500W model has lower voltage ripple on the +12V rail than the junior models, but has periodic spikes on the +5V rail. They are not dangerous at such an amplitude, though.
Fan Speed Management
The three PSUs are all equipped with the same fans. It is the D12SH-12 model from Yate Loon.
As I noted above, the senior model has a somewhat different card of the fan controller. Does it affect its noisiness?
The two junior models show the same behavior of the fan. Its speed is growing up linearly, reaching the maximum at a load of 300W. Both PSUs are noisy. The fan is audible even at minimum loads and is going to become the noisiest component in most PC configuration at loads of 150-200 watts.
Fortunately, the 500W model has a different fan controller indeed. It maintains a constant speed of the fan (1100-1200rpm) at loads below 300W and then accelerates the latter in a linear manner. This PSU might be called comfortable, if not quiet, but one of its chokes would begin to “sing” at a load of 200W and higher, producing the characteristic electric buzz. I do hope this was just a problem of the particular sample of the PSU, though.