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PSU for 6990

beardyweirdy

beardyweirdy

beardyweirdy

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Joined
6 May 2011
Posts
190
I have finally PX'd my 6950 for a 6990 but not sure my psu will run it:o
I have a Seasonic x900 from 2008 which is still a beast, but only has 6 pin pcie, not 6 +2. I will get the 6 to 8 converters in the morning but I am hoping I won't need a new PSU.
Here is a link to my PSU specs:
http://www.overclock3d.net/reviews/power_supply/seasonic_x900_ss-900hp_900w_psu/1

I am not sure what to look for re comparability so any help would be much appreciated

Cheers
 
Hmm. It's a very old PSU and the rails are quite awkwardly laid out. What I mean is you have a few 18a rails. Personally I would be a bit concerned, given that even a dedicated rail will give you 18a.

Do you know how they are wired electrically? The last thing you want to do is put more than the GPU on that rail.

Personally I would be rid of it and get something newer. Corsair 850w with single rail as a min.

It's going to become quite warm with the 6990 eating from it, considering that it pretty much tears up the PCIE rulebook.
 
beardyweirdy said:
Hi
Thanks for the reply. I am not sure how it is wired, all I know is that the literature says quad sli. It has 4 seperate pcie cables
Cheers
Click to expand...

Yeah but in 2007 things were very different mate.

Quad SLI meant a pair of 7900GX2 or whatever the first fail set up was.

Then 7950GX2.

The 6990 draws, IIRC, over 400w alone :eek:

As I say, it breaks PCIE spec.

But it's the amps that concern me more than anything. You really ideally want a PSU with a big fat single rail so that you don't have to worry about amp loads etc.
 
beardyweirdy said:
Cheers Andy
If I try using the 6 to 8 pin converter, what's the worse that will happen?
What psu would you recommend at the minute that's not gonna break the bank?
Click to expand...

Your house will burn down.

Don't play with electricity it's not very forgiving.

As I say, 850w min with a single rail. Brand can be any, but avoid OCZ. They don't make them and they have had some right old shady gits making their PSUs.

I'll have a look for you, but Corsair are a brand I would trust (well, anything but their builder series as they're plop).
 
Wow I would have thought the cosair 750 watt would have been enough but I suppose it pays to play it safe
 
Over the £15 or so? yeah, better off playing it safe.

I know PSUs bang on about 80+ but a PSU is far happier and more stable at 50%.
 
I can't see why he should change he's PSU, it's 900 watts and can deliver over 750 watts on the 12v rails alone which is more then enough for a 6990. Just because it's old it doesn't mean it's no good and besides its a Seasonic which is means it's the best make money can buy at worst he's efficiency will have dropped away but that's nothing to worry about and Seasonic guarantees it's PSU's for 5 years. Just get the adaptors and game away.
 
Freddie1980 said:
I can't see why he should change he's PSU, it's 900 watts and can deliver over 750 watts on the 12v rails alone which is more then enough for a 6990. Just because it's old it doesn't mean it's no good and besides its a Seasonic which is means it's the best make money can buy at worst he's efficiency will have dropped away but that's nothing to worry about and Seasonic guarantees it's PSU's for 5 years. Just get the adaptors and game away.
Click to expand...

Do you understand electricity?

The problem is not the wattage. Wattage - smottage. The problem is RAIL AMPS and the way the AMPS are distributed.

I recently ran quad SLI GTX 295s on a 625w power supply.

The problem with his power supply is the way the rails are laid out IE - no single rail in it is capable of pushing more than 18 amps.

Because he doesn't know how the PSU is wired electrically that means he could end up putting his 6990 on the same rail as the CPU and motherboard.

Do you know what happens to wire when too many amps are drawn through it? well, first it gets hot. Then the sheath melts and the wires touch and you have a fire on your hands.

His power supply may well be Seasonic (and I am aware of who they are and their reputation) but 18a per rail is not acceptable in 2011. It was in 2007 when his PSU was designed, because no single component drew that many amps (note my previous posts).

Load a 6990 onto a single 18a rail and you are going to get hot, fast.

My old Alienware PSU was laid out identically and I had two 3870x2 on it. It worked, but touching the PSU shell told the story. It was red hot.
 
Had to get a new psu when i got my 6990, opted for the AX850 and couldn't be happier. Very solid, fully modular compact psu.
 
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