My friend is planning to crossfire but we dont know if you can crossfire cards of different brands and clocks aswell as cards with different memory sizes (a 512 card with a 1Gb card). If anyone knows the answer could you please do.
Cheers, Fuzz
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My friend is planning to crossfire but we dont know if you can crossfire cards of different brands and clocks aswell as cards with different memory sizes (a 512 card with a 1Gb card). If anyone knows the answer could you please do.
Cheers, Fuzz
I think it takes the smalles memory size/lowest clocks
Okay easy question to answer :D
Crossfire (I assume you really mean crossfire as in ATI cards and not just the idea of having 2 or more graphics cards working together) does not require the boards to be of the same manufacturer but they need to be of the same series the is a handy chart on ATI's website (here) basically it is best to match identical cards because as Will404 said the lowest clock and memory speeds and memory buffer size will be used so adding a 1GB card to a 512MB card would be wasteful, equally if the 1GB card was really cheap it would be foolish paying more for the 512MB card.
The GPU clock and memory speeds will be dynamically adjusted when you enter crossfire mode so you do not need to buy cards with the same settings as it can/will all be adjusted by the drivers.
So basically when they are running together they will be identical in terms of speed and memory size.
Oh and while you can crossfire a 4870 and a 4830 together it is not advised as the 4870 will drop down to 4830 speeds, interestingly that would still net you a decent boost in performance but nothing like as much as a second 4870 would.
Two 4830's faster than one 4870!Quote:
Originally Posted by Webby
I would have thought that the 4870 on its own would be faster, gotta remember scaleing ect.
Yep 2x 4830's is better than 1x 4870 shocking I know but true. See the Hexus review (one of many with similar findings) http://www.hexus.net/content/item.php?item=16300
Just some follow up questions I have just thought of, if anyone could answer them would be great. Just my personal curiousity =P
1. 4870X2 (2GB) and 4870 (1GB)
a) would it work like Tri-CF 3x single 4870 therefore giving similar results if compared?
b) what happens if the 4870 is only 512MB would the memory on the 4870X2 be reduced to 1Gb (512 + 512)?
2. 4870X2 and 4850X2
would the 4870X2 just clock down to the same spec as the 4850X2 or would it just not work in the first place due to 4850X2 being a Sapphire custom design?
More easy questions (at least in theory :P)
1.a) Yes tri-fire is the result, should be comparable to 3x 4870s together maybe slightly better as the are fewer motherboards which support 3 PCIE slots all at 16x which would be easily achievable with a 4870X2 and a 4870.
1.b) and again yes the 4870X2 will drop to a 512MB frame buffer per core to match the single 4870
2. According to ATI they should work together (see the pic I linked earlier) but yes the 4870X2 would drop down to 4850X2 speeds and if you had the 1GB version of the 4850X2 the 4870X2 would loose 1GB as well. Not sure how crossfire matches the memory speeds between GDDR3 and GDDR5 though, personally I wouldn't be pairing up any non-same series cards anyway.
Just as an adendum, if you seriously have that kind of money to fry 2x 4850X2 would be a monster graphics subsystem - not only would it fly at any conceivable resolution, but you could decouple both cards for an eight monitor setup... Remarkable!