Dual single GPU cards vs. single dual GPU cards

[iamthatonedude]

I am building my first PC. I am learning some new things as I go. I realize this is likely a noob-ish question, but here goes:

Is there a performance difference between having 2 single GPU video cards with 1G RAM each in SLI/Crossfire vs. having 1 dual GPU card with 2G RAM on the one card.

For example:

Two Radeon 4850 cards with 1gig RAM each

vs

One Radeon 4850x2 card with 2gig RAM


I imagine the 2 card setup would give a performance boost having 2 slots to draw from?

 

[iamthatonedude]

okay i was reading about it a bit. i understand that with my above example i would only get the 1gig ram on a crossfire setup as having two cards doesn't double the RAM.

I also see that SLI/Crossfire doesn't benefit every game.

I am considering the 4870 and am not sure if I should go with the two seperate cards or the dual GPU card.

 

[geofelt]

The performance of the two is essentially the same.
The 4850X2 is essentially two 4850 cards crossfired on one card.
The speed of the slots currently has negligible effect on performance.

I think the single card solution is better.
If you can meet your performance needs with a single gpu card, that is the way to go.

4870-1gb, or GTX260-216 are both comparable cards at a good value.
GTX275, GTX285 or 4890 are the best single gpu cards out there today, and will run most games very well at 1920.

Only if you are using 2560 should you need crossfire/sli.

 

[Zenthar]

To me the single card solution is a bit better because, for the the 4000X2 serie at least, they added an internal communication path between the 2 GPU so they don't need to use the PCI-e bus to talk to each other and you don't need a more expensive "Full" SLI/Crossfire motherboard to take full advantage.

Then again, I also prefer a single GPU and a single card.

 

[Bluescreendeath]

SLI/Xfire makes it cheaper than getting the best single-GPU solution. So SLi/Xfire is more bang for your buck.

Single GPUs are easier to upgrade in the future, and have less driver issues.


The vast majority of games today support SLi/Xfire...only the old ones don't.

 

[Zenthar]

The vast majority of games today support SLi/Xfire...only the old ones don't.

And the same "old ones" run just fine on a single GPU anyway .

 

[coozie7]

To Zenthar (Off topic) please ignore at your descretion.
And you`d be surprised at how well they run on a mixed system (see sig). Even with the 7800GTX once mighty system killers like Doom III run smoothly on what is nowadays below even mid/entry leval cards.
@iamthatonedude: The two configuations listed would perform more or less the same, assuming a motherboard with 2 PCI-EX16 slots. The the dual card setup is less vulnerable to damage, if one card goes down, the other still runs, whereas the X2 card goes down and takes the whole graphics subsystem with it.
I`d go for a single 1Gb HD4870 and see how you go.

 

[iamthatonedude]

Yeah, it's slowly becoming clearer. I haven't updated my PC since 2002 so it's like learning all over again. Until next week when I get the rest of my parts in, I'm still on a 4x AGP card/mobo. Eeechh.

I'm going to stick with a single gpu card as I don't think I need the SLI/Crossfire. My monitor only supports upto 1920 I believe (at work currently). I'm looking at the 4890s though since I was set to spend more. Newegg has them only another $60 or so over the 4870's. Thanks for the replies, much appreciated

 

[Zenthar]

I think slowly things will go more toward parallelism. Right now with the affordable x2 cards more game publisher will require multi-GPU/CPU support as a feature (which wasn't really the case only 1 year ago).

 

[kfckfc]

One thing I considered when weighing up the pro/cons of crossfire is that with a dual card set-up I could disable crossfire and run in single card mode if I came across a game that did not support crossfire. I am not sure if you can do that with a 4850/4870X2, maybe someone on the forum can help.

 

[bboysil]

Yeah, it's slowly becoming clearer. I haven't updated my PC since 2002 so it's like learning all over again. Until next week when I get the rest of my parts in, I'm still on a 4x AGP card/mobo. Eeechh.

I'm going to stick with a single gpu card as I don't think I need the SLI/Crossfire. My monitor only supports upto 1920 I believe (at work currently). I'm looking at the 4890s though since I was set to spend more. Newegg has them only another $60 or so over the 4870's. Thanks for the replies, much appreciated

Don't pay an extra 60$ for about 10% increase in performance over the 4870. It ain't worth it in my opinion.
Just read about it here:
http://www.tomshardware.com/reviews/radeon-hd-4890,2262.html

 

[Helloworld_98]

@bboysil

$60 may seem like a lot for 10% extra performance but once you overclock it you will get more like 15-20% extra performance equalling the GTX 285 which is $110 iirc.

 

[bboysil]

@bboysil

$60 may seem like a lot for 10% extra performance but once you overclock it you will get more like 15-20% extra performance equalling the GTX 285 which is $110 iirc.

But you can also overclock the 4870 a little...

 

[geofelt]

One thing I considered when weighing up the pro/cons of crossfire is that with a dual card set-up I could disable crossfire and run in single card mode if I came across a game that did not support crossfire. I am not sure if you can do that with a 4850/4870X2, maybe someone on the forum can help.

A game that is not optimized for crossfire will use just one card. No special deactivation procedure is necessary.

SLI/Crossfire does not double the frame rates of a single card. It is more like 1.3 to 1.8 times. There is added cost for a sli/crossfire capable mobo, and a stronger psu. By the same token spending double the price of a single gpu card does not buy you two times the fps either. You get diminishing returns on your investment as you go past one good single gpu vga card. As you game at higher resolutions and more detail, the investment is a bit better. Still, how much better than 60fps in most games do we really need?

 

[Zenthar]

Worth mentioning that one of the benefit of the X2 cards is that your MB doesn't need to support XFire or SLI to take advantage of them. I don't know if they take as much power as 2 separate video cards (if so probably not by much).