Akasa Power80+ 400W... instability at low cpu power usage

[Maverickâ„¢]

I've a problem with this PSU: Akasa Power80+ Green 400 watt

it is an 80+ Bronze and in fact I've measured very low power consumption with my system:

AMD AthlonX2 4850e
Asrock AliveNF7g-HDReady (Geforce 7050PV)
1x2Gb Team Group DDR2-800
WD Caviar GP 750 Gb

idle Win XP [email protected] -> 24 watt

the issue: when underclock or undervolt CPU under those values the system become unstable and in few seconds shut down

with another PSU (old Coolermaster 350 watt passive PFC) I can go down to [email protected] and keep it for days 24/24, but the total power consumption come up to 26-27 watt and the PSU is very noisy, too noisy

so the question is: why the Akasa is so unstable at low cpu power?

thanks for the help

[Maverickâ„¢]

Nobody?

[jaganath]

read the friendly sticky:

viewtopic.php?t=30289

It turns out that high efficiency power supplies -- such as those that meet 80 Plus standards but also many others that don't -- typically need a higher minimum load on the 12V line(s) than older or less efficient power supplies.

Too low a 12V load on startup is the most common cause of a high efficiency PSU not starting with the kind of low power minimalist system that many SPCR readers build.

Usually an older or less advanced, less efficient PSU will not exhibit this problem with the same system; their minimum 12V power requirement is lower.

24W is pretty good anyway, to be honest the more you reduce CPU power draw the less efficient the CPU VRM becomes, so law of diminishing returns applies.