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What wattage of PSU do I need?

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December 30, 2010 8:28:41 PM

Hello,
I'm torn between 2 different PSUs. They are the same (?) except for the wattage (650 and 750). After, my build won't be upgraded other than an additional 6870 (at a later time). Do I need a 750 W PSU for this crossfire if im not going to upgrade for a while? Is a 650 W PSU suffice?

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

I am trying to cut corners as much as I can to keep it under $1000...

My (soon-to-be) build:
ASUS M4A89TD PRO/USB3 - MOBO
HIS H687F1G2M Radeon HD 6870 (x2 at a later date) - GPU
AMD Phenom II X6 1055T Thuban 2.8GHz - CPU
G.SKILL Ripjaws Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 - RAM
Western Digital Caviar Black WD6402AAEX 640GB 7200 RPM SATA 6.0Gb/s 3.5" Internal Hard Drive - OS and Storage
ASUS DRW-24B1ST/BLK/B/AS Black SATA 24X - DVD Burner

Also, I am going to buy an aftermarket cooler and OC the CPU a bit.

More about : wattage psu

a b ) Power supply
December 30, 2010 8:39:01 PM

Hello, and welcome to THG.

I would personally get an 800 watt...just fo more space and if you want to upgrade later. The extra wattage would give you breathing room for OC as well.
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December 30, 2010 8:47:07 PM

Well, I don't think I need that much... Aren't the 6xxx series more power efficient? Besides, the tech will be outdated won't it? Will 750W be enough to OC the CPU and GPU(s)?
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a b ) Power supply
December 30, 2010 8:50:43 PM

You'd be fine with a decent 650w running XFire.

If the card needs 2x6pin or 1x6pin and 1x8pin you will need a psu that has 4x pci-e connections for Xfire.

I'd go for one of these, they are in order of preferance, all are very capable.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Just noticed the 750w you listed was $99 after rebate and has 4xpci-e, might as well get that.
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December 30, 2010 8:57:39 PM

Thanks. I checked it though, I won't have the resources to buy all of the components by then so the cost will be $110 for me... Its not modular though and I may have a better 1st time experience with modular.
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a b ) Power supply
December 30, 2010 9:04:02 PM

The Seasonic is the best choice if you can stretch to it and modular.
Otherwise the XFX will do the job nicely and is modular for $99.
Or the Corsair 650w is in the middle, modular and has a 7 yr warranty!
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December 30, 2010 9:06:44 PM

Sounds good! If the price stays the same I'll probably get the XFX one. It does have some nasty reviews though.
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December 30, 2010 9:19:08 PM

Do you think its worth cutting out of the other components to get a 6950 instead (2GB VRAM)?
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December 30, 2010 9:20:48 PM

AND MODULAR!!! WHOOO! Do you think it'll stay in stock? (I might have to buy it now...)
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a b ) Power supply
December 30, 2010 9:26:58 PM

What do you mean cutting out? Getting 1 6950 instead of 2 6870's?

Its the same as the 1st XFX but with a grey fan that I like anyway.

Some cards need an 8 pin pci-e cable but they manufacture them as a 6pin + the 2 extras if needed.
If they made them 8 pin and your card needed 2x6 pin you'd be stuck.
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December 30, 2010 9:28:45 PM

Oh. Well I can't afford 2x 6870 right now, but I'm thinking about sacrificing on other components (like CPU) to get 1x 6950 and maybe get another later...
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December 30, 2010 9:31:04 PM

Will 620W be enough? And its not modular... Thanks though
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December 30, 2010 9:32:18 PM

Quote:
Mmm are you going to flash the 6950 bios by any chance?

Yes, but I won't OC it to 6970 Specs, just unlock the additional stream processors.
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December 30, 2010 9:42:44 PM

Quote:
The 945Be version are 20usd cheaper. Its the same chip. you pay 20usd per 200mhz. So 955 are 20usd more 3.2ghz and the 965 another 20usd more at 3.4Ghz. So if your overclocking you might aswell get the 945BE version and save 40usd by overclocking it to 3.4 yourself

Yeah but I would have to spend the $70 to buy the beast of an aftermarket cooler I want. Besides, can you reach 4GHZ with the 945Be just as stable?
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a b ) Power supply
December 30, 2010 9:43:42 PM

wigglerthefish said:
Will 620W be enough? And its not modular... Thanks though


Probably not for XFire and it only has 2xpci-e, should be ok if you decide on the 1x6950, and like you say non modular.

The XFX is cheaper with rebate anyway.

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December 30, 2010 9:47:25 PM

beanoslim said:
Probably not for XFire and it only has 2xpci-e, should be ok if you decide on the 1x6950, and like you say non modular.

The XFX is cheaper with rebate anyway.

I just saw that too...
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December 30, 2010 9:53:22 PM

Quote:
No 25usd actually.

Well I've taken a liking to the Zalman CNPS 9900MAX...
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a b ) Power supply
December 30, 2010 9:56:52 PM

wigglerthefish said:
Well I've taken a liking to the Zalman CNPS 9900MAX...


I've just got myself the Venomous X Black, I've had Zalman 9500 and 9700 but they can't live with the towers now.
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December 30, 2010 9:58:50 PM

beanoslim said:
I've just got myself the Venomous X Black, I've had Zalman 9500 and 9700 but they can't live with the towers now.

What are your temps? Maybe under Prime95. I'll check it out, but I'll stick to stock cooling (cutting corners).
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December 30, 2010 10:00:32 PM

Also, it costs more than the CNPS9900MAX... :( 
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December 30, 2010 10:06:01 PM

So would the 650W XFX work for Crossfire 6970s?
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a b ) Power supply
December 30, 2010 10:06:46 PM

Yeah I wasn't suggesting it just telling you. :D 

Anyways if you want great cooling at a decent price you can't beat the Hyper 212+.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

I'd say don't rush in just to save money, think about it and get what you know you want really even if it means waiting you'll be glad you did in the long run.

Trouble is once you start looking the options are endless and it ends up doing your head in. I know I'm still in the process off a build although I've got my components now, just got to decide on a house now. :D 

Good luck.
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Best solution

a b ) Power supply
December 30, 2010 10:11:25 PM

wigglerthefish said:
So would the 650W XFX work for Crossfire 6970s?


Its tight, probably go 750w.
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December 30, 2010 10:12:31 PM

beanoslim said:
Its tight, probably go 750w.

Back to my original choice than... Thanks for the help.
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December 30, 2010 10:18:33 PM

Quote:
Yeah it ain't modular but modular looks just a bit neater inside with the slight voltage drop you get from them. But performance wise it ain't better than non modular vice versa

http://www.techpowerup.com/reviews/NVIDIA/GTX_480_PCI-E...

Sure, it’s not 16x/16x, but 8x/8x is not a bottleneck, even for two Geforce GTX 480 in SLI

Thanks. Now THAT will save me some money!
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December 30, 2010 10:27:37 PM

Best answer selected by wigglerthefish.
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