crossfire of ati hd 6870 1gb

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waseem4690k

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Feb 9, 2015
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Plz tell me guyx how much power supply is needed to crossfire the ati hd 6870
And how much powere will it be after crossfireing.....will it be power ful like..nvidia gtx 760 or ati r9 280x or ati 280 or any other thnx in advance..
 
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VincentP

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Oct 18, 2013
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A Radeon HD 6870 card has a TDP of 150W.
Two of these with a 95W CPU and approximately 40W for other components means you will need a power supply rated at least 46A on the +12V rail.
A good quality 600W supply should be ok.

In processing power, two of these cards might get close to a GTX 760 or R9 270. Not even close to an R9 280.
The problem there though is going to be that 2 x 1GB cards still gives you 1GB of effective video memory which will limit you to low detail settings in many games.
If looking for a decent upgrade to this card, I would suggest a better single card instead.
These are listed in order of preference, better as you go down:
R9 270X
GTX 960
R9 280X
R9 290
GTX 970
 
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VincentP

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Oct 18, 2013
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121W is the HD 6850 in this article.
They found 141W for the 6870, which is consistent with the advertised 150W TDP.

You were pretty optimistic on your estimate of performance in your first post as well.
2-way Crossfire or SLI add about 60% performance when they are well supported. Many titles don't work that well with Crossfire or SLI.
The video RAM limitation is going to restrict detail settings anyway meaning the second card may increase frame rate but not really lead to improved graphics.
 
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VincentP

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This "solution" is not correct.
These cards are specified with a 150W TDP by AMD, not 175W.
The GPU performance of the two cards is at best 60% faster than single card, while the cards mentioned above are about 150% faster than a single HD 6870 (performance of x1.6 rather than x2.5).
Additionally, all these cards mentioned above have at least 3GB of VRAM while crossfire HD 6870 cards have an effective 1GB of VRAM.
 
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4745454b

4745454b

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In my defense I did say "~". If you don't know what that means, look it up. (I also said it will depend on model, as OC'd cards will be closer to 175 and not the stated 151W.) What performance you get will also depend on the game. Some scale horrible, others scale quite well.
 
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VincentP

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Oct 18, 2013
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You made the 175W figure up. It isn't hard to look up the specification. Over clocking may raise this, but if you want to put a number on it like that you should provide a link to some testing that supports your theory.

Scaling quite well is 60% improvement over a single card. That is about as good as it gets.
The idea that adding a second card can be 150% faster than a single card is absurd.
 
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4745454b

4745454b

Titan
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Oh I'm sorry mister owner of this site. I didn't read the rules you enacted to participate on this forum. I'll try to do a better job. FYI, you might want to review the rules for this site just in case YOU run afoul of any of them.

http://www.techpowerup.com/reviews/ATI/Radeon_HD_6870_CrossFire/6.html

BTW, seeing as you wanted a link, what is 373 - 190? 183W?

http://hardocp.com/article/2010/10/21/amd_radeon_hd_6870_6850_video_card_review/8

Do you see the 2560x1600 chart? 77FPS to 146FPS in CF? That's pretty close to 100% scaling isn't it?

http://www.techpowerup.com/reviews/ATI/Radeon_HD_6870_CrossFire/4.html

Here is Bad Company 2 at 1920x1200 (as close to 1080 as you'll find.) doing better then 60% as well. 53 to 100FPS. Again, nearly 100% increase. You CAN get better then 60%. It really depends on the game and resolution. It shows it faster then the 480, fast enough to probably be around as fast as a 580. Whatever that is in todays cards.
 
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VincentP

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Oct 18, 2013
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Power usage in your link is measured at the wall.
If they were getting 80% efficiency from the power supply, then 190W * 80% = 152W.
If they were getting 85% efficiency from the power supply, then 190W * 85% = 162W.

Fair enough on the benchmark. You found a game that scales to almost 90% gain from 2-way Crossfire.

From the GPU hierarchy, the HD 6870 is equivalent to the HD 7790 in a newer generation of cards:
http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107-7.html

Here is a benchmark showing both the HD 7790 and GTX 780:
http://www.bit-tech.net/hardware/graphics/2013/10/08/amd-280x-270x-260x-reviews/4
HD 7790 - 39 FPS
GTX 780 - 111 FPS

Even if Crossfire could scale at 100%, this still isn't going to get 2-way Crossfire of HD 6870 cards anywhere near a GTX 780 or R9 290. 100% improvement on 39 FPS is 78 FPS. This is absolute best case scenario, certainly not typical.
That still wouldn't take into account the difference in video memory either (effective VRAM 1GB for HD 6870 cards in Crossfire compared to 3GB+ for the other cards you suggested), which is going to be a major problem at higher detail settings in modern games.

At the end of the day it is bad advice to compare Crossfire HD 6870 cards to an R9 290, GTX 780 or GTX 970.
You would be much better off with any of these cards than the crossfire setup.
Even an R9 280X or GTX 960 is going to beat the Crossfire setup every time.
 
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