just purchased the gigabyte X48-DS5 motherboard and will be running two 4870s in crossfire. My questions is my current HD4870 is a sapphire. Unfortunately the same model doesn't seem to exist anymore 100243L. Its a 512mb card, does it make any sense to pair it with the 4870 1gig card (will it even benefit from the extra video memory in crossfire?) or just get a similar 512mb card to crossfire it with.
And no I didn't want to spend the extra cash for an i7 at this point.
If you are running crossfire the 1 gig will do you know good. In a crossfire configuration the memory on the cards isnt added together, it simply matched to the card with the lowest memory. (Meaning the 1 gig card will run as a 512 to match your current card). Your best bet is to get another 512 card, brand doesnt matter.
You won't lose that extra memory but what happens is that the cards sync together so that if one card is faster than the other (like if you pair a 4850 with a 4870) the 4870 will complete it's workload first and wait for the 4850 to finish in order to render a frame.
I am not certain, but I imagine having the extra memory in the other card will do the same thing...your 1GB card will probably complete the workload first and wait for the 512gb card to finish. You shouldn't see a gain or a loss with that setup vs two 512mb cards. It will be like having two 512MB cards...which I think is what you were trying to say.
The only loss is if you pay more for the 1GB version. You can get a 512mb card for cheaper...which I would do even if it isn't a sapphire card. Or alternatively, sell your 512 card off and get two 1GB versions. The effort probably isn't worth the return though.
Not a fan of multi-GPU setups but from what I`ve read, there`s no gain in pairing a !Gb card with a 512Mb card.
Crossfire, like SLI will work with any pair of cards as long as they are the SAME GPU. So any 512Mb HD4870 will pair with your existing card but the PAIR will work at the speed of the slowest card and (input on this point guys) set memory to match the smallest of the pair to synchronise.
So just get a 512Mb HD4870 and all will be well.