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Crossfire 7870's


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#16 Scorpian8867

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Posted 06 December 2013 - 06:55

I'm honestly not sure what to make of that given that you downplayed the issue to sound like nothing and also implied NV cards have the same problem. :huh:

AMD has been catching a lot of flack for the issue in recent years since they never offered a proper solution to fix it. nVidia jumped on it much sooner. A few years ago, they released a software-based approach as well, and then followed it up with a hardware solution. I don't know the full details of what that means, but I'd be willing to bet it's about 50% effective and 50% marketing. Whatever it is, it works, but it's not perfect.

 

* That is a little too strong. Some clever hardware engineers may make the issue a thing of the past at some point. You never know. Operate on the same clock tick somehow?

Of course, you can't eliminate it completely*, but hardware solutions do go a long way. Does NV even have frame pacing in their drivers? I'm not aware of it if they do (I can't say I've particularly looked very hard though). I think the difference in architecture alleviates the issue much on its own.

Again, they have bragged about some kind of hardware solution, but I don't know the details. I'm sure there's a software fix in their drivers somewhere as well. Even today, nVidia cards do suffer from microstuttering issues as well. It just doesn't get much attention because AMD/ATi has overshadowed them there. It's an inherent problem with any multi-GPU setup, regardless of which vendor is chosen. As you said, maybe there will be one day in the future when it's not an issue anymore, but I don't see that day on any calendar for the next few years.




#17 +snaphat (Myles Landwehr)

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Posted 06 December 2013 - 06:58

AMD has been catching a lot of flack for the issue in recent years since they never offered a proper solution to fix it. nVidia jumped on it much sooner. A few years ago, they released a software-based approach as well, and then followed it up with a hardware solution. I don't know the full details of what that means, but I'd be willing to bet it's about 50% effective and 50% marketing. Whatever it is, it works, but it's not perfect.

 


Again, they have bragged about some kind of hardware solution, but I don't know the details. I'm sure there's a software fix in their drivers somewhere as well. Even today, nVidia cards do suffer from microstuttering issues as well. It just doesn't get much attention because AMD/ATi has overshadowed them there. It's an inherent problem with any multi-GPU setup, regardless of which vendor is chosen. As you said, maybe there will be one day in the future when it's not an issue anymore, but I don't see that day on any calendar for the next few years.

 

Looks like the hardware solution was this: 

http://us.hardware.i...-adaptive-vsync

http://www.tomshardw...x2,3329-10.html

 

Moreover, looks like it worked pretty well in software (on AMD cards, next page) as well according those results so I wonder why AMD Hasn't done it this way...



#18 OP madd-hatter

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Posted 06 December 2013 - 19:20

Microstuttering in crossfire setups is nowhere near what it was back then. I've been using dual 7970's for over half a year now, and it's never been a problem for me. Especially not after the frame pacing drivers that AMD released not too long ago.

 

Also, yes, that card will work with yours. Any 78xx card will work with any other 78xx card. The only exception is the 7870 XT, which uses a Tahiti core. The R9-270 & R9-270x will both work as well since they have the same core.

Thank you. So different Sapphire 7870 cards running at 1000 and 1050mhz difference in core clock performance won't take a performance hit over say 2 identical 1000mhz?

 

I looked over the micro-stuttering article as well, I was not aware of it but not concerned with it regarding the 7800 series. Help appreciated guys.



#19 +snaphat (Myles Landwehr)

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Posted 06 December 2013 - 19:41

Thank you. So different Sapphire 7870 cards running at 1000 and 1050mhz difference in core clock performance won't take a performance hit over say 2 identical 1000mhz?

 

I looked over the micro-stuttering article as well, I was not aware of it but not concerned with it regarding the 7800 series. Help appreciated guys.

 

I don't know myself. One problem is benchmarking websites almost never do that kind of configuration



#20 Snake89

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Posted 06 December 2013 - 19:54

Looks like the hardware solution was this: 

http://us.hardware.i...-adaptive-vsync

http://www.tomshardw...x2,3329-10.html

 

Moreover, looks like it worked pretty well in software (on AMD cards, next page) as well according those results so I wonder why AMD Hasn't done it this way...

AMD got a huge slap in the face earlier this year from http://www.pcper.com/ , so right now AMD is just releasing a software fix until they can work in a hardware version an that does take sometime to fix. So maybe late next year in the next-gen of AMD graphic cards we'll see a hardware fix in place.



#21 Scorpian8867

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Posted 06 December 2013 - 20:27

Thank you. So different Sapphire 7870 cards running at 1000 and 1050mhz difference in core clock performance won't take a performance hit over say 2 identical 1000mhz?

 

I looked over the micro-stuttering article as well, I was not aware of it but not concerned with it regarding the 7800 series. Help appreciated guys.

I can't find the article to save my life, but I'm pretty sure someone tried comparing crossfire results from cards of different clocks with the same cards downclocked to the slower one. The results showed that there was still a noticeable increase despite only one of the two cards being clocked higher. This goes against the general idea that crossfire depends on the "weakest link" in the chain and is limited to the speed of the slowest card. If all else fails, you could always just overclock the slower one ot the GHz edition speeds. From what I've seen, virtally any stock 7x70 can bump right up to the GHz speeds at stock voltage, no problem.

 

Microstuttering exists on any multi-GPU setup, even 78x0-based. But again, it's a bit of an overglorified issue. Just make sure you install the latest beta drivers, and keep an eye out for new ones.

 

On that note, be prepared: multi-GPU will give you many headaches. It can work, but you'll need to be ready to fight with it. I've had to reinstall my drivers probably ten times over the past few months just because I keep encountering strange issues.