5870 tri-fire questions

[Ste]

Hi,

I bought a 5870 on release and it's been a great card - bought a second for £120 a few months ago and the difference in crossfire is amazing. I'm thinking of getting a third, partly to power 2560x1440 (on the rare occasion where 1gb VRAM isn't a huge limitation) but mainly cos it looks like a fun and geek-interesting thing to play with. I have a few questions though...

i. Would there be an appreciable difference in games like crysis 2, deus ex, etc.?
ii. My motherboard is x16/x16 PCIe 2.0 (I think - Gigabyte UDR3?) at the moment, installing a third would drop them to x8/x8/x8 I believe - any problems with that?
iii. PSU - I have a 700w OCZ at the moment that *just* copes with my 4.2ghz i7 and 2x 5870s. It dies if I try to furmark and prime at the same time What PSU would be needed for 3 of these things? Would an 850 do?
iv. Heat - in xfire one of the cards gets very warm (approaches 90'c, though a more agressive fan profile would help that). Can you actually run tri-fire without custom cooling? My airflow is excellent (Raven case) though...

Any help much appreciated!

Cheers

 

[Ste]

One final thing... is running the 3rd card from a seperate PSU something anyones ever tried? I can't see it being a problem if the PSUs are wired to come on in sync and grounded at the same point?

 

[Crezzlin]

Yeah a 850 should do fine, what model you looking at? As for 8x8x8x thats fine, prob better tahn 16x16x8 as the 16x is over kill and running at 8x is quicker latency.. I have run cards at 4x & 8x over 16x before and got better results Even the new Asus z68 flag ship board reduces the speed to 8x8x8x when running 3 cards to reduce latency

As for the performace you will see a difference with 3 cards, AMD cards scale well.

 

[Ste]

Thanks! PSU wise, hmmm, maybe this:

This Week Only Offer
Corsair Enthusiast Series TX 850W V2 High Performance '80 Plus Bronze' Power Supply (CMPSU-850TXV2UK)

Would that do the trick? I'd like it to be future proof too, i.e. run crossfire/SLI next gen cards, which I think it will. I see you run trifire too - how is the heat?

Thanks

 

[Surveyor]

Thanks! PSU wise, hmmm, maybe this:

This Week Only Offer
Corsair Enthusiast Series TX 850W V2 High Performance '80 Plus Bronze' Power Supply (CMPSU-850TXV2UK)

Would that do the trick? I'd like it to be future proof too, i.e. run crossfire/SLI next gen cards, which I think it will. I see you run trifire too - how is the heat?

Thanks

You really need something with 6 PCI-E power connectors if going with 3 cards.

That PSU has 4.

Have a gander here for the Guru3D recommendation on the power of the PSU you need.

If you're looking to future proof you need a PSU with some 8 pin PCI-E power connectors.

 

[Ovr]

Grab the OCZ 1000W Gold Plus, it's running here great (come over and see! )

 

[Ste]

My OCZ 700w only has two PCI-e, I got a couple of molex -> PCIe convertors and it's okay. Assume this would work with the Corsair too, more so since it's a single +12v rail...

 

[Surveyor]

My OCZ 700w only has two PCI-e, I got a couple of molex -> PCIe convertors and it's okay. Assume this would work with the Corsair too, more so since it's a single +12v rail...

But if you're buying a PSU specifically to run 3 cards then surely getting one with 6 PCI-E power connectors is the better option.

 

[kg648]

Silly question, but do you need 2x molex for the one PCI-e connections? or do you just need the one molex plugged in.

 

[Surveyor]

Silly question, but do you need 2x molex for the one PCI-e connections? or do you just need the one molex plugged in.

You should plug in however many the adapter has.

Some adapters have 1 molex connection some 2.