Originally Posted by pony-tail
I just ordered ( and have paid a deposit ) 2 x XFX 6870 video cards for my Re-build . First will the top card overheat ( I thought about it after I made the order - The 6870s are dual slot cards and there will be little space between them ) Second - I was informed this morning that 6870 is only about the same as a 5770 - is this true ?
I read a couple of reviews that say that it is about equal to a 5850 !
Originally Posted by Blitz6804
A single 6870 is around the same as a single 5770, but in crossfire, two 6870s are about the same as a pair of 5850s. If I remember right.
Also, I currently have a triple stack of cards and all cards stay within their specs. It could be helpful (if you have a problem) to attach a 120mm fan to blow air into the gap between the cards.
Blitz, I believe you might be thinking of the 6850, which slots between the 5770 and 5850. A 6870 routinely is above a 5850 in benchmarks I've seen (games or otherwise).
A link with theoretical comparison: all numbers.
A cross-fire pair of 5770 cards was just a touch above a 5850 for the time, and would mostly tie a stock 5870.
2x6870 cards will be a pretty good combo, and should act more like a 5970 card in terms of raw performance (6 series scales much better with Crossfire than the previous 5 series).
I checked a review here that shows a 6870 vs. 5850. The 6870 wins pretty much every time.
6850 cards, on the other hand:
Suffice it to say, 2x6870 will provide plenty of performance (I'm happy with 1x6970 myself, and even my old 5850 can still churn out good FPS). If you're having cooling issues (assuming you aren't overclocking) is it possible to put the cards in slots 1 and 3? I know this would make each slot X8, but that is all the cards need for bandwidth. Downside: you'd need to find longer Crossfire straps. If you're really not afraid, you could try liquid cooling the top card at least, or possibly both, but I would try spacing the cards apart more first...cheaper, and will probably be effective enough.
Also, in terms of your case, how many fans do you have in it, and how much do they flow? The model in your signature doesn't have all that many fans (not what I'd consider enough for the amount of airflow those cards need). Maybe try some higher flow fans to improve airflow, and be sure to provide positive airflow pressure (more intake than exhaust). If all else fails, try another case.