# 2x7970 vs.7990



## roy cline (Mar 13, 2012)

Alright TPU Gods...What would be better, 2x 7970's 3 gig in crossfire or one 7990 6 gig . I know I would be spending about 1200.00 on 2 7970s and from what i hear about 800.00-850.00  on 1 7990.  has anyone heard anything on what the talk is on this? Curious to see what the fine folks at tpu think about this. i know its going to be guess work till this new 7990 comes out but it would be nice to get your thoughts on this. also what is the choice cpu,mobo and ram to run with this set up?


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## Super XP (Mar 13, 2012)

Personally I would go with a Dual GPU card, in this case the HD 7990. The reason is in the past, all Dual GPU cards from HD 3000 series to the HD 6000 series they ran slightly faster than a Crossfire setup. Also, the Dual GPU card should have a lot less gaming and configuration issues vs. a Crossfire setup.

And you can always Crossfire that HD 7990 with another bad boy in the near future when prices go down.

Now if you didn't want Crossfire right away, than one single HD 7970 would work out fine with the option for future Crossfire. Anyhow you have the budget. 

MOBO, CPU + RAM
ASUS ROG motherboard based with a Core i7 and nothing smaller than 16GB of DDR3 - 1866 ram


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## roy cline (Mar 13, 2012)

Yeah i hear that AMD chips wouldnt unleash the horsepower that these cards will need...i dont know,im a amd fanboy but intel sounds like the way to go.


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## DOM (Mar 13, 2012)

I'm sure 7990 are going to cost more then 2x7970's


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## Super XP (Mar 13, 2012)

DOM said:


> I'm sure 7990 are going to cost more then 2x7970's


It didn't in the past if my memory serves me well.



roy cline said:


> Yeah i hear that AMD chips wouldnt unleash the horsepower that these cards will need...i dont know,im a amd fanboy but intel sounds like the way to go.


I like AMD also, as you can see from my Bulldozer setup. A high end AMD setup would cost you cheaper, and if you were to take that route, then I would wait for AMD's Piledriver.
Anyhow this time around Intel wins.


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## Dolph (Mar 13, 2012)

Im pretty sure 2 x 7970's woudl be 1 x 7990.  Im 95% sure that they each gpu on the 6990/7990/590 doesn't have the full amount of shaders and the cores aren't at a normal (7970) core clock speed.  Unless ofcourse, you get yourself an ROG Mars version of the 7990, then it would be unreal.  But as for the plain 7990 (as plain as you can call a 7990), i feel as though 2 x 7970's would out perform a 7990.  Just as, the 2 x 580 beats 1 x 590, for the exact same reason.


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## BarbaricSoul (Mar 13, 2012)

Dolph said:


> Im pretty sure 2 x 7970's woudl be 1 x 7990.  Im 95% sure that they each gpu on the 6990/7990/590 doesn't have the full amount of shaders and the cores aren't at a normal (7970) core clock speed.  Unless ofcourse, you get yourself an ROG Mars version of the 7990, then it would be unreal.  But as for the plain 7990 (as plain as you can call a 7990), i feel as though 2 x 7970's would out perform a 7990.  Just as, the 2 x 580 beats 1 x 590, for the exact same reason.



the 7990 won't be two 7970s, it will be two 7950 if history repeats itself. The 6990 was two 6950 and the 5890 was two 5850 cards. Two 7970 cards should then beat a 7990 performance wise.


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## Dolph (Mar 13, 2012)

BarbaricSoul said:


> the 7990 won't be two 7970s, it will be two 7950 if history repeats itself. The 6990 was two 6950 and the 5890 was two 5850 cards. Two 7970 cards should then beat a 7990 performance wise.



If you read my entire post you would see thats exactly what i said.  Although i see a spelling mistake that might make you think otherwise in the frist sentence...

"Im pretty sure 2 x 7970's woudl be 1 x 7990. "  I meant to say,  "would beat".  The 7990 wont have all its cores, as i said, and the 2 x 7970's would out perform the 7990. 
Aka.. final thought..
2 x 7970 IS GREATER THAN 7990


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## Super XP (Mar 13, 2012)

Dual GPU cards have been overall faster with less power usage vs. a Crossfire setup. He would be better off with a Dual GPU card. Also when Crossfire/SLI is chosen, you lose the 2nd cards RAM. The Dual GPU's RAM is their for the taking.


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## aayman_farzand (Mar 13, 2012)

I thought dual GPU cards were the same as running crossfire setups just on a single PCB? A 7970 has 3GB VRAM, so that won't be a problem anyway.

And when choosing your CPU, get an Intel, AMD hasn't made anything worthwhile in a long time.


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## lilhasselhoffer (Mar 13, 2012)

Why?

Run a single 7970 now.  There aren't a lot of games that will max this out, unless you're really going to push 3 monitors at once.

Whenever the 7970 becomes outdated get a second one.  By then the price will have dropped.  A significantly cheaper 2x7970 crossfire will likely beat out the 7990.  This is assuming that, like the 6990, the 7990 will be two 7950 GPUs crossfired on a single card.


If the 7990 is two 7970s then go with that.  The on cards crossfire removes quite a bit of latency between cards, which will produce appreciably better performance.  


Given that the 7990 is still largely an unknown, none of these recommendations are anything more than individual opinion.  Go with whatever you can afford, but given the price tag right now you may want to wait for Nvidea's Kepler.  While I'm not an Nvidea fan, this kind of pricing requires thorough thought before spending it.


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## Dolph (Mar 13, 2012)

Super XP said:


> Dual GPU cards have been overall faster with less power usage vs. a Crossfire setup. He would be better off with a Dual GPU card. Also when Crossfire/SLI is chosen, you lose the 2nd cards RAM. The Dual GPU's RAM is their for the taking.



Wrong.  Yes, they do take less power, because they aren't full GPU's, they are underclocked and un-equiped vs a regular crossfire setup.   It would be EASIER to buy 1 dual gpu card.  It would NOT be better.  

Also, the ram is indeed split between the 2 gpu's.  Notice a 6950 has 2gb of ram, and a 6990 has 4?  Do you really think, honestly, that each gpu is using 4gb?  The 7990 will most likely have 6gb of ram, 3gb for each GPU... Identical to 2 x 7970's memory usage.  Except that a7970 will take full advantage of the bandwidth/cores/shaders/everything... x 2.


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## Vulpesveritas (Mar 13, 2012)

BarbaricSoul said:


> the 7990 won't be two 7970s, it will be two 7950 if history repeats itself. The 6990 was two 6950 and the 5890 was two 5850 cards. Two 7970 cards should then beat a 7990 performance wise.


Eh no it wasn't.  It was two underclocked 6970 cards which might as well have been a 6950, it had the number of shaders of 2x 6970's.

Anyhow, I would say that if at ~$800ish the 7990 would still be a better solution price/performance compared to an X-fire setup, as even if it is 2x 7950's it would still be a better deal / $$$ as you'd get $100 off and less latency between the GPUs, and I would think it would have the number of shaders the 7970 has, so eh.  With decent Liquid cooling or a high end aftermarket heatsink you could pull off the stock speeds I would think.  If not overclock.


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## radrok (Mar 13, 2012)

Vulpesveritas said:


> Eh no it wasn't. It was two underclocked 6970 cards which might as well have been a 6950, it had the number of shaders of 2x 6970's.



I flipped the switch on my HD 6990s and I have 6970 clocks, easy as that, you just need proper case ventilation, they also overclock 1000 MHz on the core with 1.25v so there is nothing to envy from a dual 6970 unless you are going to buy custom PCBs like DCII o Lightning.


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## Shinj (Mar 13, 2012)

2 6970s or 2 7970 in crossfire will always overclock better than their "dual gpu on a single card" counterpart due to more power are being supplied to each card separately. Furthermore, the thermal solution i.e. heatsink and fan will be bigger and more efficient on a single card. Thus, always try to avoid dual gpu card if you plan to do some serious overclock


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## radrok (Mar 14, 2012)

Shinj said:


> 2 6970s or 2 7970 in crossfire will always overclock better than their "dual gpu on a single card" counterpart due to more power are being supplied to each card separately. Furthermore, the thermal solution i.e. heatsink and fan will be bigger and more efficient on a single card. Thus, always try to avoid dual gpu card if you plan to do some serious overclock



The 6990 then proves you wrong, it has a digital power delivery that can feed enough juice to both GPUs to reach maximum clocks. 

It's basically what I said on the post above, if comparing reference cards then there is no difference between 2 6970 (apart from being easily cooled than the dual GPU counterpart).

Things are different if you are talking about custom PCB.

Also welcome to TPU man


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## 20mmrain (Mar 14, 2012)

Super XP said:


> Personally I would go with a Dual GPU card, in this case the HD 7990. The reason is in the past, all Dual GPU cards from HD 3000 series to the HD 6000 series they ran slightly faster than a Crossfire setup. Also, the Dual GPU card should have a lot less gaming and configuration issues vs. a Crossfire setup.
> 
> And you can always Crossfire that HD 7990 with another bad boy in the near future when prices go down.
> 
> ...



The 6990/5970/4870x2 were not faster than two 4870's/5870's/6970's..... as a matter of fact a duel card set up (Single chip x2 different cards) destroyed all of those cards in most instances.

All the benchmarks show this.... here is a bunch of reviews stating this....

http://www.visualdreamers.com/news/radeon-hd-6990-vs-6970-crossfire/2/

http://www.guru3d.com/article/radeon-hd-5970-review-test/13

And so on....

Now if you are talking about 7990 Quadfire (x2 cards) vs 7970 crossfire (x2 cards) you would be right. But add a 3rd 7970 into that and the story changes again and the 3 card set up for the same price as the quad fire setup will destroy the quad fire.

Plus you have to take into account the rumors that have been running around about AMD lowering the clocks on the 7990 (Essentially making it a 7950x2 card) because of over heating problems. If you factor in that info..... the 7990 will most defiantly be a lower performance card than a 7970 crossfire setup.

I will take one thing back though the 4870x2 traded blows with a 4870 crossfire setup and the 3870x2 was for sure more powerful than a 3870 Crossfire setup. But those are the excptions.


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## NanoTechSoldier (Mar 14, 2012)

The Crossfire bridge, slows it down a bit, on 2x HD7970s (connecting to two seperate PCBs etc)
& it won't necessarily double the performance either..  

The HD7990, would be my option.. It's cheaper than buying two cards & all the performance, is on one PCB... Plus, you will only need one driver, to run the card too.. 

The 6GB GDDR5, is closer, to the Dual GPUs & it can cache the RAM faster etc..

Crossfire, needs more than one driver, to run both cards at once.. Catalyst + Crossfire Drivers etc..

Just be aware of the heat generated, from a dual GPU.. Install, better cooling in your case & keep that card cool...


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## manofthem (Mar 14, 2012)

I've always been under the impression that 2 6970's are faster than a 6990. This review confirms it:
http://www.legitreviews.com/article/1566/9/

Presumably similar on the 79xx cards. 

What second driver are you referring to for crossfire?  Install the AMD catalyst once, enable crossfire, and it's good to go. If you're referring to CAPs, that doesn't make sense either.


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## radrok (Mar 14, 2012)

manofthem said:


> I've always been under the impression that 2 6970's are faster than a 6990. This review confirms it:
> http://www.legitreviews.com/article/1566/9/
> 
> Presumably similar on the 79xx cards.



The GPU on the 6970 is clocked at 880 MHz and its memory is clocked at 1375.
The GPUs on the 6990 are clocked at 830 MHz and their memory is clocked at 1250, the catch is that you can flip the BIOS on the 6990 and the core goes up at 880 MHz, the only difference is that the memory doesn't get a bump but you can always overclock it and have two 6970s on a PCB.

There you have it.


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## roy cline (Mar 14, 2012)

radrok said:


> The 6990 then proves you wrong, it has a digital power delivery that can feed enough juice to both GPUs to reach maximum clocks.
> 
> It's basically what I said on the post above, if comparing reference cards then there is no difference between 2 6970 (apart from being easily cooled than the dual GPU counterpart).
> 
> ...



thanks for the welcome...i come here almost everyday and try to soak up all i can

I also appreciate all the posts, this brings a smile to my face. i like to see this type of talk and learn from it. you know ive searched other forums about this and i want to belive what they say but i have read and have seen some stuff out of here that makes this my home. I couldnt belive we havent started a thread about this yet just for chatter but i am serious about this buy dont get me wrong... love tax season. 

 i was reading from this forum 
http://forums.extremeoverclocking.com/showthread.php?t=360882
and was like hummm.. lets see what the boys say. so thanks again and keep up the good work as im like a sponge at this point and im sure im not the only one.


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## maleaco (Mar 14, 2012)

What are you going to be doing that requires such specific performance?


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## Dolph (Mar 14, 2012)

maleaco said:


> What are you going to be doing that requires such specific performance?



This is a good question, considering that the performance between (for reference) 2 x 6970's vs 1 x 6990, is marginal, i think at this point in the thread, its basically your preference and theres not really a need for a 2-4% specific difference. 

HOWEVER:, The debate going on within this thread, its 100% undisputable that 2 x 6970's are better than the 6990.  Countless reviews, logic and pure hardware state this (@stock speeds ofcourse).  Can we say this will be the case with the 7970's vs 7990?  No one can really say yes or no, its all speculation, but we can extrapolate and say that the 2 x 7970's will take the cake.  

Also, i understand that this is a pure amd thread, forgive me, but you could also consider what the nvidia specs are going to be like.


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## Shinj (Mar 14, 2012)

radrok said:


> The 6990 then proves you wrong, it has a digital power delivery that can feed enough juice to both GPUs to reach maximum clocks.
> 
> It's basically what I said on the post above, if comparing reference cards then there is no difference between 2 6970 (apart from being easily cooled than the dual GPU counterpart).
> 
> ...



Yea, you're right about the digital power delivery! 6990 can almost certainly reach 6970 clocks without too much of an hassle. However, cooling wise, two fan+two huge vapor chamber heatsinks on the 2x crossfire setup will always be more efficient than one fan+two smaller heatsinks on a dual gpu board. Thus, IMHO 2x crossfire will most of the time, if not always able to clock better than dual gpu board.

Long time reader, first time poster here 

Cheers


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## Super XP (Mar 14, 2012)

20mmrain said:


> The 6990/5970/4870x2 were not faster than two 4870's/5870's/6970's..... as a matter of fact a duel card set up (Single chip x2 different cards) destroyed all of those cards in most instances.
> 
> All the benchmarks show this.... here is a bunch of reviews stating this....
> 
> ...


The performance with Crossfire over the Dual GPU card is definitely not worth paying the $ premium. What the topic starter should do is either buy 1 HD 7970 now and plan to Crossfire in the near future. Buying 2 x 7970's is going to kill the bank unless he goes for a Dual GPU.

Right now the Price/Performance of a HD 7970 Crossfire setup in relation to the upcoming HD 7990 sucks. Also let's make something clear (Not directed to you per say), Dual GPU cards have always beaten 2 x HD 4850, 5850, 6950, etc class cards. So no Dual GPU cards are based on high end, under clocked, single GPU cards such as the HD 6970 & 7970.


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