7970 CF or 7990?

Hi guys, i just want to know from previous model which usually perform better single card in CF or dual GPU like 7990 and why?

Crossfiring independent cards is almost always faster.

The problem with current X2 cards is that they reach the wattage ceiling for a single PCIe card, so they need to be underclocked in order to stay under ~350W. On the other hand, two independent cards would be able to each use that much power, so of course there is much more headroom. A single 7970 uses something like 200-225W I think, so obviously running two of them on a single card at stock speeds would greatly exceed the max power it can draw.

i didnt done any CF before and my current VGA is 4870X2 , i usually avoid CF/SlI because if i wasnt mistaken the lane of PCI-E was 1 16X and other usualy 8X -> 4X.

what i heard you will not use the secondary card full power, im not sure about the new motherboards or new PCI-e 3.0 if this issue solved.


i have another question , what is the different between XDR2 and GDDR5 in term of performance?

Just to be clear and make sure you undestand, you ARE using crossfire with the 4870x2. It's just that the crossfire takes place on a single card. That means you experience all the same drawbacks associated with crossfire.

when u are talking about heat ~ what is the avg heat you should expect in IDLE?

currently im getting 85C no load only windows and some application but not graphical fan at auto

my graphics card is 4870X2 default clocking

Heat is the problem and is it wasn't than PSU manufactures would be making PSUs that allow the dual GPU cars like 6990 and 590 to draw all the power they could use but thermal limits is already an issue with stock air cooling which is why Radeon and Nvdia routinely under clock there dual GPU cards. Two GPUs and inch away from each other on one printed circuit board lend themselves to thermal cooling issues which is why it is always better to just get single cards for CF/SLI because then the thermal limit envelops are within spec and therefore in turn the cards can be pushed to there max limit allowable buy there respective architectures without overheating issues like a dual GPU.

it look like normal when gaming it still 80s but the fan become noise and it reach around 50~65% speed

Get Nvidia. SLI 670 would beat Xfire 7970.

570 SLI and 6950 CF are already faster than a 7970 6870 CF is as fast as 7970 currently the new cards from Nvdia will have to add tons of budget minded value for them to be competitive cause there is already ample performance available on the market for GPUs.

6990 is two undervolted 6970s and all ready even being undervolted heat is an issue so how does 8pin 105watts and 6pin 75watts PCI-E power have to do with anything when the thermal design is just inefficient even when underclocked and volted on dual GPU cards which is why they are flawed LOL.

Electrically produced heat is a waste by product of inefficiency hence why typically newer cards are more powerful using less energy and heat. The 80+ PSU certification explains thermal efficiency very well. http://en.wikipedia.org/wiki/80_PLUS in short Heat output and power draw are directly influenced by the efficiency of the GPU architecture for example GTX 480 vs GTX 580 the GTX 480 creates lots more wasted heat energy because it was very inefficient.

Are you a moron? Have you bothered to read anything? The PCIe standard does not let them put 4 8-pin connectors on it! At most they get two, and 300W! That is it!

You're also convinced a 560 Ti is slower than a 6870, though, so I guess I should take it easy on you. It's not nice to make fun of the mentally challenged.

http://pcper.com/image/view/6686?return=node%2F52216