Nominal vs. Peak Power? Help!

[Stangs55]

Okay...so I just bought a brand new Thermaltake Ultrapower 550W PSU. (At least that's what it says on the box).

However, when I opened it, the fan control panel has 480W written on it. So I raised my eyebrows and checked the side of the box. In the specs, it says:
Nominal Power: 480W
Peak Power: 550W

Uh....what's this mean? Did I just buy a 480W PSU and now realize it? Can I get a consistent 550W? Is there a difference btw this and other brands (Enermax, for example)that advertise 600W? Do they have a 'nominal power' as well?

Sorry if this is a stupid question...but I'm just a lil' confused. I don't want to bottleneck my new 6800 Ultra!

Thanks in advance.

 

[Ice Czar]

Can I get a consistent 550W?

no
http://www.pcguide.com/ref/power/sup/output.htm
http://www.pcguide.com/ref/power/sup/outputPeak-c.html

but then you likely dont need it either
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cut and paste 101

http://takaman.jp/D/index.html?english

and use the values listed here for newer graphics cards (you can manually add them into the calculator above) make sure to use the additive result of the power supplied from the AGP slot and the auxillary power to the card, the total isnt given on the charts
Power Consumption of Contemporary Graphics Accelerators. Part I: Graphics Cards on ATI Chips
Power Consumption of Contemporary Graphics Accelerators. Part II: NVIDIA vs. ATI

and double check the processor value against this database
http://users.erols.com/chare/elec.htm
if there is an auxillary +12V power connector on the mobo, add it to the +12V rail
if not add it to the +5V rail

and follow the instructions here for other considerations (like temperature)
Whats dont mean Jack
I generally deduct 1\3rd off the amps a PSU is rated
to reflect the difference between the temperature it was tested at 25C
and the normal operating temperature in the enclosure 40C,
because its typically exhausting the HeatSink

as the title suggests, it aint the watts that is important
its the proper distribution of amps to the various rails

forgot to mention inputting a value for a CPU is a little different, since the database is simply listed in consumption in watts (max) what you have to do is add in a guess as to the Amps in either the +5V or +12V box (select other CPU not listed from the drop down menu)
that will give you the watts to the right, so, by trial and error adjust the amps to the watts to match the database figure

or just convert the watts to amps with a calculator first
AMPS = Watts / Voltage

so an Athlon 64-3200+ with a Thermal Design Power figure of 89W being powered off the +12V rail...

89 divided by 12 = 7.41Amp
which is really close to waht is listed in that calculator
(88.8 watts and 7.4A)

also note the utilization box at the top, that simply applies to the search returns whan you look for compliant PSU, not the figures listed
since many manufacturers lie like dogs regarding their specs
its best to post a thread regarding what supplies your considering
also that is a Japanese site, and some of those brands wouldnt be readily available here
and some we have arent listed

that would give you the theoretical maximum
that reflects the nature of any calculator
its additive of all the maximum draws for each component
but all components rarely if ever need their maximum draw at the same time

for instance a HDD may require 2A on the +12V line at spinup to overcome inertia
but only .05A while spinning, same for fans high amp draw at spinup
(not using the opticals, then you just have a very low standby draw)
the opposite applies to an IC (CPU/GPU) from Idle to load
for example figures for an X800XT (one of the most power hungry GPUs and cards)

525/1150
............................IDLE...........................LOAD
+3.3V.......1.05Amps 3.48Watts................2.71Amps 8.74Watts
+5V..........1.42Amps 4.05Watts...............3.33Amps 16.75watts
+12V........0.85Amps 10.09Watts..............3.25Amps 37.73Watts
Total W.....17.62Watts Idle.......................63.23Watts load
which jumps even more with an overclock
550/1250...18.43Watts Idle.......................65.88Watts load
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there is considerable differences between makes
and that peak rating is deceptive, (and worse at 40C)
to determine what supplies are actually putting out you really need to research the specs, some manufacturers are more prone to marketing bullsh!t than others, Thermal Take, OCZ come to mind
while others are pretty straight with the facts and actually provide decent specs, Enermax, Antec, and probably the best out there PC Power and Cooling (they actually rate their supplies at 40C so the 510s are actually 600 watts in a comparision to other manufacturers)