GPU Upgrade: Radeon 6870 + 6850 hybrid or 6970?

[sephirotic]

Ok first of all i'm not a native english speaker so please excuse any mistakes. Also, i have already spent a reasonable amount of time searching on the forum and google about similar cases of mine and found only contraditory and vague information about Hybrid Crossfire, not to metion my case is a tad more specifical.

Simple put, i would like to upgrade my computer for better graphical performance on games. (specially: Arma II and III, BF3, F1 2011 and some gorgeous games like Crysis 2)

I already have the current computer:

Corsair TX650, A 6870, an i5 2500k Running at 4.4ghz and a ASUS P8P67. (yes i know about the 16x4x, it isn't an issue with the level of performance of the 6850.)

I have the equivalent of 260 USD dollars, but in pratical, on my country, due to taxes, GPU cards end being much more expensive. (instead of 350 USD a 6970 actually costs 500 here, very sad indeed)


I have two options with my budget:

A) Get a 6850 and crossfire with my already existing 6870

B) Sell my 6870 and buy a single 6970 instead.

Lots of questions around perfomance and issues regarding the first option:
I've find lots of contraditories information regarding the Hybrid crossfire. (or would it be mixed? Dunno about the correct nomenclature)

1) The performance is actually notable bigger than a simple 6850 + 6850 regular crossfire. (True?)
2) Shader cores even tough in different numbers are NOT CAPED down and are added. (True?)
3) DIFFERENT CORE FREQUENCY WON´T BE A PROBLEM and the 6870 WON´T DOWNCLOCK to the equivalent performance of 6850, only MEMORY CLOCK (and amount) would be limited since textures need to be loaded equaly on both cards. (True? This is the most condraditory affirmation yet, because apparently test of older generations, 48xx and 58xxx worked differently with out of dated drivers less optimized for crossfire and lots of people talks with autorithy based on older experience with those crossfires with are not relavant to this actual case)

4) Micro stuttering: What i REALLY would love to do is actually crossfire my 6870 with a 6870x2 sice i've read here in Tom's that micro stuttering got completely eliminated with a 3 6870 setting. But there is not a single 6870x2 to sell on my country not to mention they exorbitating prices here, imagine paying a premium of 900USD on a card). How bad REALLY is micro stuttering? Bad enough to make buying a single 6970 a better option even with a theoretically 30% lower performance than the crossfire setting?

Thanks in advance for all the help and please excuse my english mistakes and if i'm out of the forum rules. I really did not find compealing information on my specific scenario.

EDIT: Ow, forgot to mention, my target resolution is 1920x1080@60hz.

 

[beltzy]

Lot's of folks are concerned about microstuttering. Basically it's quick, large jumps between min and max framerates that have the potential for users to perceive the slowdowns/speedups in the framerates. I used HD 5850's in crossfire (similar performance the 6870s in crossfire) and really haven't ever noticed the problem. It is, however, pretty subjective and we all want consistent performance, not large peaks and valleys.

Here is the url for the TH article: http://www.tomshardware.com/reviews/radeon-geforce-stutter-crossfire,2995.html

Honestly I'd recommend you try to push your budget just a bit and get another 6870. The additional money will not only be additional performance, but your current 6870 will utilize all of it's performance (instead of slowing down to match the 6850).

 

[SinisterSalad]

I agree with a 2nd 6870. I'm running two currently. It's a beautiful thing. I do not experience microstuttering with the latest drivers in BF3, either.

 

[sephirotic]

(...) I used HD 5850's in crossfire (similar performance the 6870s in crossfire) and really haven't ever noticed the problem. It is, however, pretty subjective and we all want consistent performance, not large peaks and valleys.

Here is the url for the TH article: http://www.tomshardware.com/reviews/radeon-geforce-stutter-crossfire,2995.html

Honestly I'd recommend you try to push your budget just a bit and get another 6870. The additional money will not only be additional performance, but your current 6870 will utilize all of it's performance (instead of slowing down to match the 6850).

Honestly I'd recommend you try to push your budget just a bit and get another 6870. The additional money will not only be additional performance, but your current 6870 will utilize all of it's performance (instead of slowing down to match the 6850).

I did read this article before, and as far as i understand, the problem is agravated when the fps is low (30~40fps). If i play with reduced graphic options seeking a 60fps frame rate it'll be hardly to notice correct?



Unfortunetely the difference in price of the 6870 to 6850 is too big to justify the first option (around 120USD from 6850 to 6870 here), so it's hardly an option. Also, as i've researched and posted on my initial post, it is a myth to think that an 6870 will be caped down to a 6850 on an hybrid crossfire, performace will actually be superior. (How much, however, is a mistery since no benchmark apparently exist comparing a 6850 x2 6870 x2 and 6850 + 6870 hybrid).

 

[kilo_17]

Performance with a 6870 and a 6850 will indeed be faster than a single 6870. But, when CrossFiring, if you have 1 faster card and 1 slower card, the faster card will be slowed down to match the slower card. You will still get better performance in games, but, the 6870 will be slowed down to 6850 speeds. In my opinion, I would add a 6850 anyway, even though it would slow down the 6870. The fact that performance will be better than a single 6950, and the fact that you would have to go through the hassle to sell the 6870; adding a 6850 gets my vote.

 

[sephirotic]

Performance with a 6870 and a 6850 will indeed be faster than a single 6870. But, when CrossFiring, if you have 1 faster card and 1 slower card, the faster card will be slowed down to match the slower card. You will still get better performance in games, but, the 6870 will be slowed down to 6850 speeds. In my opinion, I would add a 6850 anyway, even though it would slow down the 6870. The fact that performance will be better than a single 6950, and the fact that you would have to go through the hassle to sell the 6870; adding a 6850 gets my vote.

Kilo, please tell me what is the source of that information.

i've researched a lot about this matter and apparently this only happened in the old 4xxx series, nowadays the performance of two different AMD cards isn´t leveled on the lower one, only Memory bandwidth. Different Shaders and core speeds are scalled in a smarter way.

This however is not confirmed, no recent benchmarks seen to exist and i would like people that affirm one thing or another provide links to support they claim. I'm here EXACTLY because so many people in different foruns and threads simple affirm one thing or the other without any solid proof. I couldn't come to a conclusion of who is right and if the scalling of two different cards in cross is in any good.


This is driving me mad!

Sorry if i am being too picky, but is my money after all.

 

[spentshells]

Sell the old card and buy something new. Avoid any future issues by doing the easy thing.

 

[sephirotic]

Sell the old card and buy something new. Avoid any future issues by doing the easy thing.

Yeah, is always better to have a single fast card than two slowers one, but unfortunetely my budget is limited and i want the best i can have with it.

Also even tough i CAN sell my 6870 this would take time and i would lose money. Not to mention i have TWO desktops in my house and eventually puting the 6850 on the older desktop (wich actually is pretty decent: And q6600) would be interesting when friends go home.

Is that a problem for you if i don´t have much money and want to use it with the best performance possible?

 

[kilo_17]

To be honest, I never looked into it, I've always believed the slower card will bring down the faster card, and I still do. I really don't see why you should sell the 6870, it's not "old" by any means. Add a 6850 and enjoy the increased performance, imo.

 

[sephirotic]

To be honest, I never looked into it, I've always believed the slower card will bring down the faster card, and I still do. I really don't see why you should sell the 6870, it's not "old" by any means. Add a 6850 and enjoy the increased performance, imo.

I always assumed that, that is why i tought buying a 6850 would be a wast of my 6870 extra potential. But recently i've read some people defending that no, the part of the extra performance of the 6870 would be used, specially the extra shaders.

I think it is odd, how could they synchronize two differente Core speed and performance? Maybe some very clever optimization in the Drivers, who knows? I couldn't find any test to back that theory.

In anyway, a 6850 crossfire would already be excellent compared to a single 6970 so i shouldn´t think about the waste, instead, think about the GAIN i would have with the crossfire.

But then i got blocked in the micro stuttering issue.

Ow Dear.

 

[wolfram23]

First off, adding a 6850 would be a very inefficient thing to do. Essentially you'll wind up with CF 6850s as the 6870 would need to limit it's performance. Obviously that's a waste of cash. Might as well return the 6870 and get two 6850s... however, I would definitely suggest if you can to just go buy the 6950 2gb instead. If you get a Sapphire Toxic edition it comes with a dual BIOS switch, so you can even attempt at unlocking it to a 6970.