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How is crossfire currently?

J

jordan12

[H]F Junkie
Joined
Dec 29, 2000
Messages
11,053
I got a new MB that has crossfire. It is still the S775 though.

I have one 4870. Does crossfire work well enough to try it? Or is it simply a major main in the ass?
 
works great, but don't expect to have support for it when new games come out.
 
rennyf77 said:
works great, but don't expect to have support for it when new games come out.
Click to expand...

No support? I don't have any problem with any new game so far.

And CF scales pretty well. Expect 150-180% performance.
 
Anandtech did an article on Crossfire and SLI scaling quite a while ago. For the 4870 crossfire scaling then was between 60-95%, and I'm fairly certain scaling has only improved since then. Of course, there are a few games where multi-GPU setups don't work very well at all, but for most games it will be very good. I'm actually thinking of getting another 4870 myself.
 
The thing about it, for some reason they are scaling now on games they the 48xx series had a problem with such as crysis and arma II.
 
exe163 said:
No support? I don't have any problem with any new game so far.

And CF scales pretty well. Expect 150-180% performance.
Click to expand...

some posters say cf doesn't work in aion, i don't play mmo's so i can't attest. 5870 cf is significantly inferior to 4870x2 cf in re5. i just posted numbers on that yesterday. when the 9.10's come out this month, i expect that situation reversed. but this is pretty typical for ati not to have the proper drivers ready when a significant product appears on the market, even their own.
 
rennyf77 said:
some posters say cf doesn't work in aion, i don't play mmo's so i can't attest. 5870 cf is significantly inferior to 4870x2 cf in re5. i just posted numbers on that yesterday. when the 9.10's come out this month, i expect that situation reversed. but this is pretty typical for ati not to have the proper drivers ready when a significant product appears on the market, even their own.
Click to expand...

/facepalm, did you not get the memo... about the beta drivers for 9.10?
 
twit. what drivers do you think i'm using. but guess what? the 5870 still gets savaged by the 4870x2 in re5.
 
i love ati hardware as much as anyone but i'm not going to drink the kool aid. furthermore, civility is a two way street ladies and gentlemen.
 
So does that mean I might have support for new games? Or is it kind of out there to just find out as they are released?


I have read in a few places that with crossfire enabled, that some game performance can actually be slower than if you have just one card..Is that true?
 
jordan12 said:
So does that mean I might have support for new games? Or is it kind of out there to just find out as they are released?


I have read in a few places that with crossfire enabled, that some game performance can actually be slower than if you have just one card..Is that true?
Click to expand...

CrossFire is not a feature like PhysX or EAX which requires a developer to include support, its just SMP for GPUs, which means it has to conform to the rules of SMP (ok its more akin to ASMP but whatever.), in other words, Amdahl's law, which means scaling will NEVER be 2.0x and will ENTIRELY hinge on the ability of the given task to be parallelized

hence why you see 60-95% performance gains with an additional GPU, it depends on the application being scaled, some games are fairly friendly to being spread out over other processors, and you can approach 2.0x, some games don't respond very well at all, or their performance is so abysmal to begin with, that the jump isn't much (think about it, ~60% of 1 isn't that much)

now, based on averaging maths, and general "guesstimation", I'll normally tell users its +0.7 per GPU, in other words if you have one GPU it will give you 100% of its performance, if you have two, you get 170%, this is ON AVERAGE, some applications are better, some aren't (as explained above), as far as applications being SLOWER than a single card, this is an issue of driver optimization (driver quality plays heavily into the application being parallelized due to how the whole mess works (technically you could say this is all part of the application being computed)), AMD and nVidia have gotten very good at working this out (basically its "slower" because the extra GPUs can't leverage any advantage, so the performance hit is a result of the compute overhead on ~0% performance gain), so that you will either have parity with a single chip, or a minimal gain

another issue/point to make, is that going over two GPUs presents some interesting findings, while the +0.7x statement generally holds true, the gains are usually pointless (as I say: if one can't run it, two can't, and if two can't, three or four DAMNED surely can't), but you do have a lot of extra processing power, which means extra features (what I'll call "vender specific IQ widgets"), which are things like SLI-AA and 3D Vision from nVidia, and EdgeDetect AA from AMD, become possible (for example a single 4870X2 cannot generally handle 24x Edge-Detect AA playable, two 4870X2's will usually get you 60-80FPS or better with the same settings enabled)

based on this, I generally don't suggest 3-4 GPU setups unless you've just got a lot of cash to spend on extra widgets, although for extra performance, adding a second GPU is a great upgrade if you've got the money and pre-existing hardware (in your case, you said you do, so ~$120 for a 4870 is a better deal than $400 for a 5870 (both would get you roughly the same performance))

honestly I'd go for it, assuming your current solution is underpowered for your existing display or IQ wants
 
those are the instances when the driver engineers haven't gotten around to writing a profile for cf. for a major release it usually only takes one refresh to get things sorted out, but some games never get supported. mirrors edge is a game i often use to illustrate my point because it trails in comparison to nvidia multi gpu setups. the game runs on unreal 3 and shouldn't be so difficult for ati hardware match nvidia's
 
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