PSU - How Big Would I Need?

[guptasa1]

Building a new machine soon, and worst case scenario (meaning all of these high-end parts...may end up being lesser), how much of a PSU would I need? Is 1000 watts overkill...will, say, 850 work with room to expand? 750?

Also, what about fitting in that Lian Li case - any issues with, say, the Enermax Galaxy series?

And finally, does a PSU actually use 1000W whether it needs to or not? Or does it use whatever the system draws?

Thanks!

Parts I'm leaning towards at the moment:
Lian Li PC-V1200Aplus II Aluminum Case (3x 120mm Fans - Front, Rear, & Side)
ASUS Striker Extreme Motherboard (680i; Nice Heatsinks Built In)
Intel QX6700 Quad Core CPU Retail (Stock Cooling)
2X GeForce 8800GTX XXX Edition (Stock Cooling)
4 GB Memory (Still Deciding...May Have Cooling if Crucial Dominator)
Possibly a Sound Card & Physics Card Eventually
2 WD 500 GB SATA HDD
DVD-RW Drive
DVD/CD Drive
Floppy Drive

 

[myocardia]

This one will run that system, with a bit of reserve (which is what you want in a psu): PC P&C Silencer 750. As a matter of fact, it's already validated by nVidia to be able to run SLI'd 8800 GTX's. It's also the cheapest you'd likely be able to get away with using.

 

[Operandi]

The 600 watt Seasonic M12 would have no problems running that system.

 

[The Sauce]

I think you should probably get a backup generator for your house though - otherwise your lights will all dim when you start that thing up.

 

[guptasa1]

You're sure 750 would be sufficient? I found a PSU calculator (http://www.extreme.outervision.com/psucalculator.jsp) and at full load (though a few things I guessed on, like fans and such) it seemed to indicated I could use as much as 808...

And secondly, is it a real danger with a machine this powerful (connected to a UPS most likely) to blow out the circuit breaker? I have 550W on my current system, and with that, the entertainment center running, and the vaccuum cleaner, I already tripped it (I think it was the vacuum mostly...but still).

And I also still need to know...does a power supply rated at 1000W actually consume that much all the time, or only the power that's needed? For example, say the system only needs 500 watts at a given time...is that the power actually consumed, or does it take the full 1000?

 

[LiquidFlame]

No one needs a 1k PSU, theres no reason to get one. What you guys are looking is wrong, Watts are important, but you really need to look a the total Amps on +12V rails. For example, if your going to use 2 8800GTX's you need a PSU that supplies no less then 56 Amps across the +12V rail. Read these two post and then you'll be pretty educated on what you need.
http://forumz.tomshardware.com/hardware/PSU-101-ftopict198276.html
http://forumz.tomshardware.com/hardware/PSU-Reference-List-ftopict222154.html

 

[Operandi]

Read this and this.

Your questions should then be answered.

 

[Dunbar]

Originally posted by: guptasa1
And I also still need to know...does a power supply rated at 1000W actually consume that much all the time, or only the power that's needed? For example, say the system only needs 500 watts at a given time...is that the power actually consumed, or does it take the full 1000?

First off, I'm not even going to get into why someone would SLI two 8800's. But to answer your question, no a 1000w PSU does not use that all the time. That is the maximum wattage rating, most of the time you will be using far less than that. As far as tripping your circuit breaker, a more powerful computer is only going to exascerbate the problem. Try not running everything at the same time I too doubt you need a 1000w PSU, a good quality 750 should be just fine. Check newegg reviews to see what other SLI'd 8800 users are having success with.

 

[happy medium]

Originally posted by: guptasa1
Building a new machine soon, and worst case scenario (meaning all of these high-end parts...may end up being lesser), how much of a PSU would I need? Is 1000 watts overkill...will, say, 850 work with room to expand? 750?

Also, what about fitting in that Lian Li case - any issues with, say, the Enermax Galaxy series?

And finally, does a PSU actually use 1000W whether it needs to or not? Or does it use whatever the system draws?

Thanks!

Parts I'm leaning towards at the moment:
Lian Li PC-V1200Aplus II Aluminum Case (3x 120mm Fans - Front, Rear, & Side)
ASUS Striker Extreme Motherboard (680i; Nice Heatsinks Built In)
Intel QX6700 Quad Core CPU Retail (Stock Cooling)
2X GeForce 8800GTX XXX Edition (Stock Cooling)
4 GB Memory (Still Deciding...May Have Cooling if Crucial Dominator)
Possibly a Sound Card & Physics Card Eventually
2 WD 500 GB SATA HDD
DVD-RW Drive
DVD/CD Drive
Floppy Drive

Thats a high power system with a heavy price tag. I Say, if you got the money just buy it!!! You won't need to upgrade it for 3 years at least. Just make sure it fits. If not grab a Thermaltake Stacker case.

 

[guptasa1]

Thanks. If I go with this rig, I suppose I might as well go with the 1000 given it doesn't actually use more power if it's not required but I'll have it should I need it.

I am considering a non-SLI machine now though, which should mean 750 should be more than adequate if I go that route. Decisions, decisions - this is hard! LOL.

 

[guptasa1]

Just as an FYI, I did some more research and am beginning to learn a lot more about power supplies.

For future reference, and this was already said here before but makes more sense to me now, things like the Galaxy 1000 would NOT be good for this system! It isn't designed with enough power going to the 12V rails for high-end video cards. Additionally, I guess modular power supplies aren't great for these cards either, despite them being convenient, since modular automatically means more resistance.

So now I'm considering other brands using this list:
http://www.slizone.com/object/slizone_build_psu.html

 

[Conky]

Originally posted by: myocardia
This one will run that system, with a bit of reserve (which is what you want in a psu): PC P&C Silencer 750. As a matter of fact, it's already validated by nVidia to be able to run SLI'd 8800 GTX's. It's also the cheapest you'd likely be able to get away with using.

This recommendation is the smartest. The PC&P 750 Silencer is gonna run it all and is about as cheap as you are gonna get for a top of the line PSU.

 

[guptasa1]

Hmmm...plus the copper color is very pretty and I'm gonna have a windowed case. Whether 750 will be enough down the road if I upgrade vid cards, I dunno (so it's tempting to go for 850), but...I'm reading that 750 really should be more than sufficient for quite a while... Most things I've read are estimating I'm not even probably going to be using more than 600W most of the time. So you guys don't think I'd be shortchanging myself at all a bit down the road with 750?