Plz clear my confusion about gpu & psu

Hi guys,
I am little bit confuse about what psu to buy for 5770.
As i am going to make

i3 540
p7h55-v
2 or 4 gb ddr3
80 gb old hd ( for some time cuz i am low on budget )
Ati 5770 1 gb


On different forums & youtube reviews, i saw some people saying 5770 consumes only 18 watts when idle & consumes onle 108 watts when on max load. My question is that, On 5770 specifications it is written that it needs 450 watts atleast. so why are they saying it consumes 108 watts on max load?
should i use 460 watts psu or a normal 400 cooler master or a cheap one will be ok? if yes then why?

1 thing more,
Can any one tell me what are rails, Amps & volts on psu? what they are for ( i am ashamed of asking such questions cuz i am totally & completely a noOb)

Another question,
if i have 400 watts psu & i use 2 gpu of any kind which needs 400 watts psu. i need 800 watts psu for them or 400 watts will be supplied to both??
i think you know what i wanna know.

see,
if i have 400 watts
i have 2 components of 100, 100 watts and a gpu of 400 watts ( total is 600 watts), so from 400 watts .. 200 watts will be left or it will still provide 400 watts to my gpu if my gpu?

i am too much confused guys plz help me

It can be confusing , especially when Gia adds his response to a thread.
Most of the power needed by your PC components comes from the 12v rail/rails, like I said in your other thread 16 amps from a 420 watt psu is crap.
What you need to concern yourself with is the amps available not the total wattage of the unit.
A good 400-450 watt psu is plenty for your system as specced above.
http://www.newegg.com/Product/Prod [...] 6817139017
http://www.newegg.com/Product/Prod [...] 6817371006

I would go with a 600W or higher.

Why ?

18 amps could do it for your PC , I'm just not into low amperage, low quality power supplies, I like to leave more room for upgrades.

The current office system builds I provide consist of
I3-530
P7H55-M LX
2x2g DDR3
HD
OD
No videocard , not needed for these applications
Antec EA380 / Corsair 400 , depending on which has the better deal at the time ( either of these would work for you as well )

Prime 95 causes a draw from the wall of ~82 watts ( AC ), that's roughly a 65 watt ( DC ) load, if you have a psu that can maintain 80% efficiency at such low loads.

The 5770 has been shown to draw ~106 watts ( DC ) when stressed with Furmark.
http://ht4u.net/reviews/2009/amd_a [...] index9.php

Add 'em up, 171 watt load on the psu, just a bit under 18 amps when stressed with the power viruses.

You really don't want to run a psu close to it's max all the time ( obviously wouldn't unless you were running just the PV's, but gaming can bring you close )

I think I explained that in my last post

aaaaaaaaaaaaaaaaaaaaaah em crying beleive me

I am using Firefox. I have also noticed that the links do not work when you click on them. I have noticed that they do work if you right click and select "Open Link in New Window".

Why?