6950 Crossfire

[hubbs_67]

Hello,

I bought a Sapphire 6950 2 Gig a few months ago and was considering picking up a second.

It's my understanding that when you run cards in Crossfire, that only the memory of the "main" card is used - could someone confirm if this is accurate?

What I'm really getting at - is it worth it to buy a second 6950 2 gig card, or if I save a few bucks and buy the 1 gig am I not going to notice a difference at all if it's only going to use the 2 gig memory on the "main" card which I already have? (ie - does crossfiring only effectively double the graphics processing power or does it also double the memory available?)

Thanks in advance to any replies!

 

[jjb8675309]

if you already own a 2 gig and you buy a 1 gig then you will have 1 gig available for both cards, so that would not make any sense. Get a second 2 gig if anything, but first what are yoru full system specs so I can let you know if your system coudl keep up, I had crossfire 6870s and honestly from my personal expirirence they worked like crap, my system couldn't keep up/ the poor minimum fps that was caused from crossfire by nature drove me nuts... The sporadic microstutter was not worth it to me so I sold them and upgraded to a single 570. One of the other problems was the my p2 955 @ 4.0ghz was not enough to have a large enough overhead to control 2 gpus and I believe that this was also a contributing factor to the stutter but my point is that I would not recommend runnning high end crossfire on an am3 setup so list you full specs including psu make and model and I will give you some further input. I am just speaking from my personal experience, and I know that minimum fps would be a bit better with the 6950 but I'm just warning you of some of the shortcomings that I experienced...

 

[hubbs_67]

Hehe, yeah my current set-up definitely couldn't keep up - running a Wolfdale E8400 OC'ed to 4 Ghz, but am looking to upgrade my system in the near future and was considering adding a 2nd graphics card in the process. Still researching and haven't selected 'exact' components at this point, playing with the budget. Definitely going Sandy Bridge K series on the CPU, either i7 or i5 depending on price and a minimum 750 watt PSU.

So if I bought a 1 Gig card, even though I would have 3 gigs total and a card with 2 gigs on board, it would default to the lesser of the two cards and I would only effectively have 1 Gig? That's the dumbest thing I've ever heard, does AMD have monkeys writing their drivers these days?

 

[jjb8675309]

yeah you would have 1 gig total, but still more gpu muscle, I think a SB build would be great for crossfire but as I stated before I won't be xfiring for a while bc imo it does not work as advertised (At least not with 6870s).

 

[diatribe]

Both cards use there memory. It's not as though memory sits unused on one of the cards. They share processing and memory resources either by splitting frames between them or rendering alternate frames.

 

[jjb8675309]

yeah but they both use the same 2 gig frame buffer, you will not have 4 gbs to work with in the case of the OP but otherwise I agree with you

 

[hubbs_67]

On the hardware reviews, this site often recommends crossfiring two cheaper cards to get "better performance" than one (ie, two 6970's are supposed to be a much better solution than a single 6990 if you have the room for two cards), but you are saying the crossfire doesn't work as advertised... are the hardware reviews on this site misleading about crossfire then? I don't have a 2500 x 1600 display so the huge frame buffer isn't a big deal for me, but from reading the reviews I was thinking that two 6950s in crossfire would be the best thing since sliced bread for a 1080p or 1200p set up....

 

[jjb8675309]

yeah i am saying that in my personal experience it did not work as advertised, although I did have 6870s not 6950s... the bottom line is that amd does not pay much attention to their crossfire drivers and many have abandoned x fire setups for sli or a single powerful setup. In my own experience I had terrible micros stuttering and low fps which is caused by the nature of crossfire... in theory 2 6950s should be great if you have a 890fx or better motherboard and imo you need better than an am3 setup to begin with in order for the cpu to have enough overhead to control 2 powerful cards with settings cranked up at 1080p. Bottom line now I have a single gtx 570 oc'ed to 580 levels and at 1080p I am more than happy and it has lower avg frames then my 6870s in crossfire but the overall experience is much better bc of high minimum fps which is something that benchmark sites hardly ever speak of and imo it is very important to the overall experience

 

[jjb8675309]

what are your full system specs>?

 

[topper743]

jjb8675309 Stated
"The sporadic micro stutter was not worth it to me so I sold them and upgraded to a single 570. One of the other problems was the my p2 955 @ 4.0ghz was not enough to have a large enough overhead to control 2 gpus and I believe that this was also a contributing factor to the stutter but my point is that I would not recommend running high end crossfire on an am3 setup"
Hugely broad statement.

jjb8675309 stated system.
AMD phenom II x4 955 (clocked at 4.0 ghz)
2X2 gig corsair 1600mhz ddr3
XFX Black edition 650w psu
MSI 890gxm-g65 mobo
Hitachi 1 tb hd 7200rpm
dell 22\" lcd 1920X1200
6 120 mm case fans
1 140 mm case fans
hyper 212+ cooler w 2 fans
CM Storm Scout
PNY GTX 570
Lite-on DVD drive

The 955 comports itself fairly well against any current desktop cpu available today. Look a any benchmark from any source and the 955 does well especially for its price point losing out to $1000 chips from Intel at stock specs by only a few frames in most games. Remembering that most of these games are TWISTBP Intel and Nvidia optimized. Most users have not been able to get their over clock to 4Ghz so I congratulate you, I do wonder if running the cpu so far out of spec really helps the part. Most Cpus have a sweet spot where they will produce the best benchmark scores and since yours is a rare one to hit 4GHZ I wonder if the graph of performance would show yours to be at its peak point. Since you mention micro stutter I took a look at your system config and the 650 PSU stood out to me as a possible problem. Is it very new? PSUs are subject to capacitor aging resulting in reduced output. Those 9 fans you say you have from your sig by themselves would suck a lot of power as well as two GPUs during peak load especially if they are LED fans. Since you say that with one card you now have no stutter the PSU or some other factor related to your system setup may be a factor as two cards will use more power than one.

The bottom line is that your statement any AM3 chip is unsuited for crossfire is too broad to be supported anecdotally from just one system. BTW a 6950 ($230) BIOS upgraded to 6970 performs very much on par with a 570 ($324). Do take a look at this benchmark tool it is helpful in comparing apples to apples or oranges.

http://www.anandtech.com/bench/Product/102?vs=47

 

[jjb8675309]

lol yeah the psu is more than adequate, it is practically brand new and my fans are not high performance nor led and now im actually just running 4 fans bc of my new case having beter airflow besides that low end fans are not goign to draw much power. also it was 6870s not 6950s that I was running, I run my 955 at 3.8 24-7, and yeah you need something better than than for high end crossfire, the point is that along with the microstuttering the drivers caused several other problems pertaining to colors and flickering. Minimum fps is a product of midrange crossfire (6870s) by nature although with two in crossfire I was getting significantly less minimum fps from dual cards then I was with a single card.. this is rediculous and ruins the overall expiriecne imo, Bottom line if you are going for a high end crossfire setup such as 6950s then I would go with something along the lines of an i5 2500k, the 955 is fine for any single card but when you add a second the cpu need more overhead to control two cards, on top of that in myt personal experience amd's drivers are ***. To the OP Id unlock your existing 6950 or add another if you think your system can handle it, again I had 6870s so I can't speak for the 6950s but I would think with the 6950s the minimum fps would be a little better but overall its going to suffer from similar problems as the 6870s did, Ive heard many people on this forum complaining about crossfire but never sli, sli seems to work as advertised, yeah 6 series crossfire scales better than 5 series sli, but not by much and also sli brings higher minimum fps which is a big deal for me. I could go on and on detailing my problems but honestly its exhausting so I hope this helps to explain my situation a little better and by no means am I biased towards either side, I just go with what works best for the money... and in the end I will choose quality over quanitity

 

[topper743]

JJ, your particular experience with your particular model cpu is out of the main. Something in your setup is incorrect, whether it is an actual bad part or something in the setup that is hindering the performance. Based on what you are saying your experience is I would say that we can discount that system as a representative one of the class. Please look at the benchmarks link I provided or any others for that matter. A 955be $139) oc'd to 3.5GHZ (a la a 970be at stock) outperforms a Intel I7 975 extreme ($1049) at 3.33GHZ in 15 of 37 benchmark tests. Most reasonable persons would stipulate that real world applications are a better test of an electronic parts' performance versus a synthetic benchmark. I am not saying that the 955 is superior to the 975x. My Point still is that you are making too broad and factually incorrect statements. Additionally I think that you are unfairly maligning a cpu that has a place and designed purpose that for most users fits that purpose very well functionally and economically. A system with a 955be and two high end GPUs will run very well assuming that all the components are functioning correctly and the system is properly configured and cooled.

 

[jjb8675309]

yeah my cpu was fine, crossfire minimum fps sucks, crossfire drivers suck, single powerful card/ sli = a much better overall expirience. My config is properly set up and cooled, lol... you can think that I do not know what I'm doing but I do..

Do you have crossfire? have you ever used dual gpu configs?

you cannot deny that minimum fps makes for an overall terrible expirience...

I have had many people who agree with me except for those that own a 5 series or low end 6 series crossfire setup...

drivers aside I think the 6970 or 6950 in crossfire is not bad but still has significantly lower minimum fps then 570 or 580 sli...

I know my CPU was more then fine....

I guess im just warning people of the issues assosiated with crossfire these days, the flickering, microstutter, poor drivers, poor minimum fps, and single one of these things would be a deal breaker for me and unfortunatley they all exist

think about a single 6870 pull minimums around 28-30 in a demanding games such as crysis, well add a second card and now your damn near 20 fps minimum or less which is a huge swing from the avg fps you get..

now take the 6970 for example at least that card will start off with a better minimum fps overall and only be decreased by a small amount when adding a second card..

So, therefore I conclude that crossfire (although I will not be attempting it for a while) shoudl only be done with high end cards, and if someone wants a virtually headache free dual gpu setup, sli is the way to go...

 

[topper743]

hubbs_67, if your first card has 2 GBs and you want a second card then get a card with 2 GBs also.

 

[jjb8675309]

^yes agreed

 

[hubbs_67]

Best answer selected by hubbs_67.

 

[jjb8675309]

psshh I write this huge explanation that is completely ignored what an asshole

 

[Mousemonkey]

This topic has been closed by Mousemonkey