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Would I be able to get ATI HD 5850 crossfire on my rig?

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August 19, 2010 1:49:58 PM

Hiya, my PC specs are:

Windows 7 64-bit Home-premium
Intel Core i5-750 @ 2.67GHz
Corsair XMS3 6gb DDR3 RAM OC @ 2140GHz
NVidia 8800GT 512mb @ Stock Clocks
ASUS P7P55D-LE Motherboard (which I believe does support ATI CrossFire set ups, but not NVidia SLI sadly)
750w PSU (I don't know the exact make and model, but I know the correct wattage)

As you can see, my GPU is falling behind modern standards and is currently the bottleneck of my PC, so I've been considering upgrading to 2 HD 5850s in CrossFire configuration. What I need to know is whether or not it would be worth it for me, and whether my PSU and computer in general would be able to handle 2 such cards. My case has pretty decent airflow too, being a tower case with a 25cm side fan and I believe another 12.5cm fan at both the front and back.

I used the PSU calculator and worked out the required power supply WITH the HD 5850s in CrossFire, and with everything taken into account, it suggested a minimum power supply of 514W (so I'm guessing my 750W is definitely reasonable for the cards?)


P.S not sure if it's irrelevant or not, but here is the card I'm thinking of getting in CrossFire configuration:

http://www.dabs.com/products/xfx-ati-radeon-5850-725mhz...

Thanks guys, any help is much appreciated! :wahoo: 

More about : ati 5850 crossfire rig

August 19, 2010 2:26:52 PM

You should have no problems running a Crossfire setup with your configuration.
August 19, 2010 2:48:20 PM

Xfire will be no prob as your power supply has enough power...(I have a pair of XFX 4890's in xfire that run in an x8/x8 config on an Antec 750watt PSU). The only problem that I foresee is that you will not benefit from the most performance in xfire with your board as it will run in a x16/x4 mode even though your 2nd PCIe slot is an x16 slot the bandwitdh on it is only x4.
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August 19, 2010 2:53:29 PM

sl83r said:
Xfire will be no prob as your power supply has enough power...(I have a pair of XFX 4890's in xfire that run in an x8/x8 config on an Antec 750watt PSU). The only problem that I foresee is that you will not benefit from the most performance in xfire with your board as it will run in a x16/x4 mode even though your 2nd PCIe slot is an x16 slot the bandwitdh on it is only x4.


Hmmm so what kind of problems would that bring? Would it impact performance massively do you think? Why is it that the second slot will only run in x4 mode? :/ 
August 19, 2010 3:23:02 PM

Also, would I be better off simply getting an HD 5970, which runs for roughly the same price?
August 19, 2010 3:34:43 PM

X16/X4 takes abut 25% performance from you GPU, and since Crossfire scales by the slowest caRd, its not really worth it.
August 19, 2010 3:49:06 PM

I agree with Timop. Definatly go with 5970 if you can, you will see much better performance. As for the x16/x4 issue, I believe that is a limitation of the chipset on your mobo. Or it can simply be the way ASUS decided to make the board. :D 
August 19, 2010 3:49:59 PM

sl83r said:
I agree with Timop. Definatly go with 5970 if you can, you will see much better performance. As for the x16/x4 issue, I believe that is a limitation of the chipset on your mobo. Or it can simply be the way ASUS decided to make the board. :D 

P55 can scale X8/X8, ASUS just enabled that via software on more expensive boards.
August 19, 2010 3:56:35 PM

Timop said:
P55 can scale X8/X8, ASUS just enabled that via software on more expensive boards.

Right, they do that to differentiate models. That and sli costs them a royalty fee to use.
So the more expensive model they put the inexpensive switch IC to split the 16 pci e lanes available to 8-8 and then name it sli/crossfire ready.
The 16x/4x board actually uses all 16 lanes in the pci-e controller built in the 1156 chips, and gets 4 more lanes from the actual p55 chipset. Sata III/usb3 sometimes uses some lanes from either source depending on the motherboard.
August 19, 2010 4:21:26 PM

notty22 said:
Right, they do that to differentiate models. That and sli costs them a royalty fee to use.
So the more expensive model they put the inexpensive switch IC to split the 16 pci e lanes available to 8-8 and then name it sli/crossfire ready.
The 16x/4x board actually uses all 16 lanes in the pci-e controller built in the 1156 chips, and gets 4 more lanes from the actual p55 chipset. Sata III/usb3 sometimes uses some lanes from either source depending on the motherboard.


Thats true of the p55 i forgot...idiot me...lol :non:  my p45 does x8/x8 scaling
August 19, 2010 4:54:56 PM

Ahh thanks a lot everybody! I guess the fact I went for the Light Edition of the MoBo to try and shave of a few extra £££s was probably not the best idea, but I think I'll probably go with the HD 5970 given what you guys have said.

One last question though, do you think my processor would bottleneck the HD 5970 at all? Is it worth perhaps overclocking it?
August 19, 2010 4:58:23 PM

I would actually recommend dual GTX460s and a new Mobo, comes out cheaper and with a little room to grow.

Though an 750 shouldn't bottleneck a 5970 in GUP-bound games, maybe in CPU intensive games. But it OC amazingly and I would do it anyways.
August 19, 2010 5:03:16 PM

talminator said:
Ahh thanks a lot everybody! I guess the fact I went for the Light Edition of the MoBo to try and shave of a few extra £££s was probably not the best idea, but I think I'll probably go with the HD 5970 given what you guys have said.

One last question though, do you think my processor would bottleneck the HD 5970 at all? Is it worth perhaps overclocking it?


CPU no bottleneck as i mentioned before i have 4890's in x8/x8 congif with a Core 2 Quad Q6600 @2.4ghz(stock speed). No bottleneck with that combination at all.
August 19, 2010 5:31:36 PM

Timop said:
I would actually recommend dual GTX460s and a new Mobo, comes out cheaper and with a little room to grow.

Though an 750 shouldn't bottleneck a 5970 in GUP-bound games, maybe in CPU intensive games. But it OC amazingly and I would do it anyways.


Originally I was considering a GTX 460 SLI setup, until I found out my MoBo doesn't support NVidia SLI, and I'm a bit reluctant to fork out for another MoBo just yet when I only got this one a few months ago. I'm definitely considering what you said about OCing the i5-750, as I've heard that's a great thing to do anyway. I'll probably try and find a few guides online, since I'm new to the processor overclocking scene :) 

The only thing which tempts me about the HD 5970 (as powerhungry as this may sound) is the 2gb GDDR5 video memory, in comparison to the 768mb/1gb that I could get with a GTX 460. I just wonder whether getting 2gb of memory would be a more futureproof idea?
August 19, 2010 5:35:01 PM

talminator said:
Originally I was considering a GTX 460 SLI setup, until I found out my MoBo doesn't support NVidia SLI, and I'm a bit reluctant to fork out for another MoBo just yet when I only got this one a few months ago. I'm definitely considering what you said about OCing the i5-750, as I've heard that's a great thing to do anyway. I'll probably try and find a few guides online, since I'm new to the processor overclocking scene :) 

The only thing which tempts me about the HD 5970 (as powerhungry as this may sound) is the 2gb GDDR5 video memory, in comparison to the 768mb/1gb that I could get with a GTX 460. I just wonder whether getting 2gb of memory would be a more futureproof idea?

2 1GB GTX460s cost $440, plus a $160 SLI Mobo its only $600, $60 less than the HD5970.

Note the 2GB of the HD5970 is really 1GB. they're listing the total amount of memory onboard, but remember in CFX/SLI you can only utilize one cards Vram. For a real 2GB youll need those 4GB 5970 cards.
August 19, 2010 5:39:53 PM

Oh okay, that does actually make good sense. So the '2gb GDDR5' is more of a marketing ploy than anything else, since only 1gb will be used properly. I presumed they meant the card had 2gb of accessible video memory. :) 

In which case, I think I might go with NVidia on this one, and either go for dual 460s in SLI, or wait and see if NVidia can produce anything in the form of perhaps a GTX 495 dual-gpu card to knock ATI out of the water to save me the extra cash on a new MoBo. Plus I'd get the added joys of NVidia PhysX ;) 
August 19, 2010 5:41:40 PM

talminator said:
Oh okay, that does actually make good sense. So the '2gb GDDR5' is more of a marketing ploy than anything else, since only 1gb will be used properly. I presumed they meant the card had 2gb of accessible video memory. :) 

In which case, I think I might go with NVidia on this one, and either go for dual 460s in SLI, or wait and see if NVidia can produce anything in the form of perhaps a GTX 495 dual-gpu card to knock ATI out of the water to save me the extra cash on a new MoBo. Plus I'd get the added joys of NVidia PhysX ;) 

The do that with almost all dual GPU cards. XD

If you want to wait, why not wait a extra month or two to see how the HD6000 are, it could turn out to be great.
August 20, 2010 3:59:29 PM

Not a bad idea. Or maybe if NVidia can get in fairly quickly with a GTX 600 series (presuming the 500 will be mobile graphics again), though I'm not overly hopeful about that since the 400 line-up is pretty recent.
!