How much power do I need?

Tetras said:
As I said in my first post I think a decent PSU in 500+ model range would be sensible. Your PC would have been sucking most of that out of the +12v rails and even if we take a PSU universally(ish) recognised as decent, the VX450, it is only rated up to 33A / 396 Watts.

http://www.corsair.com/products/vx.aspx

Yes a 400 Watt PSU would run in the short-term but I don't think it would be leaving enough headroom and end up running harder than I'd be comfortable with (especially considering PSU is an investment that will potentially last through several rigs / upgrades).
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i would imagine the ten120mm fans, 3 hard drives, 4 sticks of ddr800 and a host of usb devices were sucking a fair chunk from the 3.3 and 5v rails too, actually. an 8800gtx only needs about 13A from the 12rail under load @ stock. a cpu uses probably 60-80w typically (for an overclocked c2d like mine was) or about 6.5amps. plenty of headroom in a decent ~400w psu like the corsair, there. dont forget, that was 330w draw from the mains factor in the ~84% efficiancy of my cpu, and the components would have been drawing closer to 275w from the psu.
 
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plenty of headroom in a decent ~400w psu like the corsair, there
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And efficiency is optimum without excessive headroom but even with your figures I stand by my recommendation, model in 500+ range :p
 
I never reuse my PSU's. So far I have had 4 PSU's, enermax 485w, nexus 350w, nexus 400w and a corsair 520w. All of my PC's have been 3 years old atleast though (excluding latest one).
 
Just been on Nvidia support, and official requirements for

8800GTX are:
Minimum 450w PSU with 12v @ 30 amps.

8800GTS
minimum 400w with 12v @ 26 amps.

Which says to me, you should be looking at PSU's in the 500-600watt range if you dont want to stress the PSU too much, and retain a decent ammount of efficiency.
 
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mattyfez said:
Just been on Nvidia support, and official requirements for

8800GTX are:
Minimum 450w PSU with 12v @ 30 amps.

8800GTS
minimum 400w with 12v @ 26 amps.

Which says to me, you should be looking at PSU's in the 500-600watt range if you dont want to stress the PSU too much, and retain a decent ammount of efficiency.
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thats for the entire system! a decent 600w pue like the 620w corsair would (and has done) power two gtx's in sli with a quad core.
 
so what are you trying to say then'? psu's reach the highest efficiancy with about 65-70% output typically. not that there's a lot in it - the corsair 620w is >80% efficiant from ~220w load right up to a 600w load, peaking at about 84%

a pc drawing 270-odd watts from its psu will not stress the psu if its rated at 400w. recommending a 600w psu is absolutely overkill! as long as the power distributing is right from the psu, you can happily use something far less powerful (and far cheaper).
 
Im not reccomending a 600w PSU,
Im saying that Nvidia, the people who make 8800GTX's, recommend a minimum 450w PSU with 12v @ 30 amps....
I dont think its terribly presumtuous and assume there will also be a processor, motherboard, RAM, a few HDD's etc. also involved in the equation.
 
yes, thats the minimum they recommend based on the types of components they think people will be running along side the graphics card. ive already mentioned before the gtx needs about 13amps from the 12 rails at stock, thats pretty common knowledge thats leaves another 17 amps for the cpu and.....what else draws heavily on the 12 rail?

james.miller re: my old system draw of 330w at the mains said:
i would imagine the ten120mm fans, 3 hard drives, 4 sticks of ddr800 and a host of usb devices were sucking a fair chunk from the 3.3 and 5v rails too, actually. an 8800gtx only needs about 13A from the 12rail under load @ stock. a cpu uses probably 60-80w typically (for an overclocked c2d like mine was) or about 6.5amps. plenty of headroom in a decent ~400w psu like the corsair, there. dont forget, that was 330w draw from the mains factor in the ~84% efficiancy of my cpu, and the components would have been drawing closer to 275w from the psu.
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james.miller said:
what else draws heavily on the 12 rail?
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Well, if we take the corsair vx450 as an example, corsair tech support state that the 12v rail is rated at 33amps, and not to put a combined total of more than 30 amps onto it.

If your planning on filling out your system, then things start looking a bit tight in terms of amps on the 12v.

OC'd intel proc 8a
OC'd GTX 15a
hdd1 .5a
hdd2 .5a
hdd3 .5a
optical1 1a
optical2 1a

Total 26.5 amps, allowing a safety margin (for config changes and peaks of power ) brings it right up to the rated ammount of amps on the 12v, so to me that means the specs of the corsair 450watt PSU are the absolute minimum (also re-itterated by Nvidia themselves) you would want to use in this kind of system.

For the sake of flexibility and general prudence, you would have to really look at the HX520 (or simmilar)
 
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mattyfez said:
Well, if we take the corsair vx450 as an example, corsair tech support state that the 12v rail is rated at 33amps, and not to put a combined total of more than 30 amps onto it.

If your planning on filling out your system, then things start looking a bit tight in terms of amps on the 12v.

OC'd intel proc 8a
OC'd GTX 15a
hdd1 .5a
hdd2 .5a
hdd3 .5a
optical1 1a
optical2 1a

Total 26.5 amps, allowing a safety margin (for config changes and peaks of power ) brings it right up to the rated ammount of amps on the 12v, so to me that means the specs of the corsair 450watt PSU are the absolute minimum (also re-itterated by Nvidia themselves) you would want to use in this kind of system.

For the sake of flexibility and general prudence, you would have to really look at the HX520 (or simmilar)
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Rock On :)

I love it when a post comes along which actually looks like it's based on research.
 
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8800GT @ 700/1800/1000
E6600@ 3.4 1.47 load 1.55 idle
2 HDD's, 1x IDE 160, 1x SATA 320

Will the above specs even be pushing my HX520W?
 
Well I would say thats a pretty sensible PSU for that spec, although Im sure others will beg to differ.
If by pushing it you mean "is it straining under the pressure?", almost certainly not.
But thats the Idea, is it not, to have a decent safety margin, and having a load thats substantial enough to keep the PSU ticking along nicely within its comfort zone.
 
yes corsairs and similar decent brand will do that all day long, and their rated out is at 50c as well

MMc2K3 said:
Rock On :)

I love it when a post comes along which actually looks like it's based on research.
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was that referring to me? because i *actually* measured my own pc and tbh, it doesny get much more accurate than that:)

MMC2K3, your figures are already worst case draws dont forget. i think its obvious that anybody really pushing a gtx or a quad should look at psu's with higher outputs - thats why i have a 620w corsair. but for all the worst case figures you are giving us,k dont forget that corsair themselves have told us that the 620w will run an overclocked gtx sli/quad rig and have demo'd one doing so.
 
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Spec in sig works great on a Tagem 580W & the combine warning light only comes on when clocking the my old B3 at 3.6.

I think all this talk about needing a big PSU is hokum.
 
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