CrossfireX and 4800

Scerick

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Is it possible to run a 4870 and a 4850 in crossfire? Or was I misunderstanding the way CrossfireX is supposed to work.
 

Scerick

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One more question, if you could.

My motherboard is a 16x/4x configuration. Would 1 4870 beat out the 4850's in xfire since I can't do 16/16 or 8/8 mode?
 

topper743

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Get the 1 4870 since you have just the one 16x slot. You will have alot of power without the possible snags. What CPU do you have?
 

SpinachEater

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Yeah you are going to take a hit with the x4 in xfire. Let me see if I can pull up the THG article where they tested this. Like topper says, with one x16 your best bet is to go with a more powerful single card.

What resolution do you use?
 

doomturkey

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I'm pretty sure the 4870 won't downclock. Crossfire x is meant to allow mismatched GPUs work together.
 

SpinachEater

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I am trying to look that up. I am doubting myself now if it actually downclocks or not. The cards have to be normalized in output in order to have a smooth performance. So it doesn't make sense that one card will perform faster than the other in xfire.

If the faster card doesn't downclock, the end effect will act like a downclock where the 4870 would somehow get inhibited to the speed of the slower card.

Edit: Topper you are right, there isn't a downclock. I am still trying to tack down some info on what happens to the faster card.
 

topper743

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Downclock might be an inpercise term. In CF or SLI the cards take turns rendering the display. Triangle A is done by card 1 and triangle B is done by card 2 and so on. The cards have to by definition render at the same rate. If one card is on a 16x slot and one card is on a 4x slot they must run at the same rendering speed. The end result is a dual 4x speed. Scerick one consideration is that if your MB is a 16x and a 4x setup it is doubtfull that you could get the full benefit from two cards as the MB is dated and crippled for the CFX that you have in mind. Again I vote for the fastest single card you can afford while using that MB. At 16x10 a single hd4870 will push the highest fps that your CPU can manage assuming that the CPU is the same era as the MB.