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Mobo won't post with two 470gtx

Last response: in Graphics & Displays
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March 5, 2011 9:38:10 PM

Here's what I have currently:

Asus P5N-E nForce 650i with an e6750
4x 1G DDR2 800
2x 350G HDD, 1x 1TB HDD
800w psu
evga 470gtx 1280

I've been slowly building towards a new pc, picking up components when I have the money. I'm saving the new cpu/mobo/ram purchase (since they all have to be at the same time) until later this year, probably at the end of the summer.

However, I recently picked up a matching 470gtx since I'll ultimately want to run 2 in my next system, but I also thought that I could run them in my current system as well.

So, here's the problem...

I can insert either gpu by itself on my mobo and my pc will boot fine. However, when I flip the sli selector card to dual and plug them both in, my pc won't post, no display at all, and I get 1 long beep followed by 3 short beeps - which ASUS says indicates a video issue. I've tried unplugging everything but my main HDD and the 2 gpus, removing all but 1 ram stick, etc. but it just won't work with the 2 cards.

From looking around on google, I'm thinking it's one of two things. Either my psu isn't cutting it (I have 2 separate 12v rails for pci-e, one at 20A, one at 22A) or my mobo is having issues. Each 470gtx requires 38A, so I'm guessing I would probably be at the psu's limits, but I think it should at least post. I've also read many threads by people with the Asus P5N-E having trouble running a variety of different cards in SLI. It is an older board, and really not ideal for 2 of these giant cards.

I just wanted to get some opinions on whether it's the psu or the mobo or something else entirely, or if anyone has had any experience with this mobo running 2 newer power-hungry gpus.

Thanks!

More about : mobo post 470gtx

March 5, 2011 9:49:17 PM

id say the psu is your problem.
which one do you have?
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March 5, 2011 9:57:42 PM

It's a realtively cheap XION 800W Real Power, not the modular version.
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March 5, 2011 10:03:06 PM

hmmmm... something tells me it may be a power supply problem.
you said it works with one 470 but not both of them together.
i guess your psu is JUST not powerful enough.
would you like a suggestion of what psu to get? (and where to get it from. eg newegg, amazon, etc)
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Best solution

a c 225 U Graphics card
March 5, 2011 10:10:10 PM

Though the SLI zone lists "certified PSU's as low as 700 watts for twin 470's, two 470's really want an 850 watter if you OC'ing.

http://www.slizone.com/object/slizone_build_psu.html

I'd suggest the XFX Black Edition 850 at $130 as the cheapest of the 1st tier (10.0 performance rating on jonnyguru.com_ PSU's.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.jonnyguru.com/modules.php?name=NDReviews&op=...

unless you have an Antec 1200, P183, P193, or DF-85 in which case I'd suggest the CP-850 ($120)

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.jonnyguru.com/modules.php?name=NDReviews&op=...
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March 5, 2011 10:29:53 PM

Thank you for your thoughts, guys. So, if I were to go ahead and get a new psu now that would ultimately go into a newer system this fall with an i7 SB or similar, should I go ahead and go with a solid 850W psu, or something with more punch?
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March 13, 2011 5:35:54 PM

Best answer selected by dwalsen.
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