How much power do I need?

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ChorniyVolk

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Sep 1, 2009
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So I'm making a new build, it'll be an i7 920 overclocked with an aftermarket HSF, 6GB DDR3 RAM, a soundcard, and one newest gen ATI card, haven't decided whether to go 5870 or 5850 yet, but I'd also like to leave the option of Crossfire open for the future. Apart from that, I'll have 4 HDDs and 1 SSD, and everything else is just standard, you know, a few case fans here, a dvd burner here, etc.

How big a PSU would I need?

Also, what companies should I aim to buy from? I see some great deals occasionally from places like tiger direct for 700w-800w PSU's at extremely low prices, but it's always some company called Ultra or something like that. Who can I trust 100%? Is there a tier list for PSU developers? Who's at the top?

Oh, and if you can do me the kindness of suggesting a good PSU as far as Price : Performance, I was hoping not to spend more than $120 or so (though those deals, and even the occasional one on newegg really brings that down to $80 or so, if not less, as far asdecent PSU's that I've seen).

Thanks a lot.
 
dualsmp

dualsmp

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HOOfan 1

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Sep 2, 2007
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Originally posted by: ChorniyVolk
Really? You're sure I can stick with 750w and be fine?
Click to expand...

As long as you aren't going nuts with overclocking and use a quality PSU...I would suggest the Antec TPN 750W.
 
dualsmp

dualsmp

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Aug 16, 2003
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Yeah don't cheap out on a PSU and then possibly fry two 5870's. The Antec Truepower New TP-750 that H00fan recommended for $95 bucks AR is a good buy. Even qualifies for 80plus Bronze which is good.

Antec Truepower New 750W -- Jonny approved. :)
 
yh125d

yh125d

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Dec 23, 2006
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OC'd i7, 5870 xfire possible in future, any good 650w+ would be fine. I'll also recommend the Antec since I have one ;)
 
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ChorniyVolk

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Sep 1, 2009
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Alright, I'll put all of those up for consideration (including the 850w, it's also on newegg for the same AR price), will take any more suggestions or deals, but it looks like I'm one step closer to finishing my build.

Any comments on the 850w though? Is it better in every area compared to the suggested 750w's? Because considering the price, it seems awesome.
 
yh125d

yh125d

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Dec 23, 2006
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Originally posted by: ChorniyVolk
Alright, I'll put all of those up for consideration (including the 850w, it's also on newegg for the same AR price), will take any more suggestions or deals, but it looks like I'm one step closer to finishing my build.

Any comments on the 850w though? Is it better in every area compared to the suggested 750w's? Because considering the price, it seems awesome.
Click to expand...

I assume you're asking about the corsairs? The TX line is a bit under the HX line in efficiency and stability, 750w or 850w doesnt seem to matter. The Antec TPN is somewhere in between the TX and HX for eff/stability, but costs as much as the TX line or less which is what makes it such a good deal with the TPN Blue for $105 shipped to your door, or $95 AR shipped for the non LED


One thing I'd add about the TX line, if you're not going to be using the majority of the massive amounts of cables on it, you're gonna have to shove all that extra somewhere, and that def takes up space. One guy on here built a rig with a TX750 in an antec 1200 and was complaining that they took up too much space
 
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HOOfan 1

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Sep 2, 2007
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The TX850 is better in pretty much every aspect than the TX750...although the TPN are better performers, better efficiency and better ripple suppression. The TX850 performs as well as any PC user would ever need though.
 
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ChorniyVolk

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Sep 1, 2009
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So these are the only ones worth considering? The top of the line for what I need as far as price : performance and quality?
 
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HOOfan 1

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Sep 2, 2007
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Originally posted by: ChorniyVolk
So these are the only ones worth considering? The top of the line for what I need as far as price : performance and quality?
Click to expand...

Not the only ones worth considering....but yes some of the best as far as price/performance.

Let me put it to you this way, you are not going to find a decent 750W+ PSU for under $90...and even at $90 for a quality unit, the vendor is likely selling it under cost.
 
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ChorniyVolk

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Sep 1, 2009
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What about $120, that's what I mentioned my budget was, with that in consideration, these are all I have to pick from, yes?

I'm just trying to make sure I have all the contenders before I make the choice.
 
yh125d

yh125d

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Dec 23, 2006
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For $120, yeah these are a few good ones

TX750
TX850
HX650 (sometimes drops under 120 with rebates and sales)
Truepower 750
 
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HOOfan 1

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Sep 2, 2007
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Unless you can find some insane deals...yes those are the best options for $120.

With the prices I am seeing now the TPN 750W is the best of them all for under $120 at straight before rebate status.
The TX850 can't compete as far as efficiency or ripple suppression but its after rebate price of under $120 and the extra 100W make it a good deal too.

The TPN is very very partially modular and the TX850 isn't modular at all.
 
yh125d

yh125d

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Dec 23, 2006
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Yeah I'd agree again with HOOfan, the TPN really is the best option. Slightly better eff/stability, partial modularity (the only hardwired cables you wouldn't really be using anyway are the 4 pin CPU and maybe the second PCI-e), cheaper after rebate, and cheaper even than the corsairs after for the LED
 
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ChorniyVolk

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Sep 1, 2009
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Yeah, I suppose the extra 100w isn't a big deal, I'm not planning to go crossfire soon anyway (the 5870 destroys most stuff by itself as it is).

Thanks for the help, I really appreciate it A LOT!
 
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ChorniyVolk

Senior member
Sep 1, 2009
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Modelworks

Modelworks

Lifer
Feb 22, 2007
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The way to figure up power required is pretty simple. Sites like AMD say things like 650Watts but that is the entire pc. So to break it down.

amps x volts = watts.

The 5870 card uses just under 200watts per card, so roughly 12V @ 17A per card. So if you want to do two in the future you need 12V @ 34A for just the cards.

Hard drives are at most 12v @ 1A . With 4 hard drives that adds 4A to the 12V requirements, so now we are at 38A. Add another 1A for SSD drives for 39A total.

Cpu like the i7 920 peak at 130W or 130W / 12VDC = 10.8 ~ 11A, brings it up to 50A.

DVD burners max out at 2A on 12V , now 12v needs 52A.
Motherboard uses about 8A for 12V , brings us to 60A.

So at the very least nothing less than 12V@60A needed. And you really want to have a bit of headroom over that so the supply isn't maxed. I would look for something 65A or better.
 
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