Any news about 3870 and 4870 CrossFire compatibility?

[Giacomo]

Just as the title says...

I'm wondering if, when the 4870 cards are out, I'll be able to CrossFire one of them with my 3870.

Giacomo

[zanzabar]

it should work since they are both going to be crossfireX but the 3870 michg be dropped to physics

[Giacomo]

it should work since they are both going to be crossfireX but the 3870 michg be dropped to physics

So is it really a known fact that every CrossFirex card will be compatible with all previous generations CrossFirex cards?

Giacomo

[AliG]

No, with crossfireX any current ati card can be crossfired within its own family. So you can crossfire a 3870 with a 3870x2 and what not, but you can't xfire a 3870 and 4870 (as far as we know, there may be a way down the road once its actually launched) as they are not part of the same generation, let alone family

[zanzabar]

the r6xx and r7xx are in the HD family

[xMrBunglex]

afaik, AliG is right. i don't think you can CF a 3870 and 2900 either. you can CF a 3850, 3870, and 3870 X2 if you have enough room on your mobo though.

[zanzabar]

u can do 2900 and 3870 ive done it, it works, i think that anand also has it

[dng]

zanzabar:

how do you crossfire a 2900xt with a 3870? i love to know how as i have a 3870 and a 2900xt. please note that the 2900xt is the 1GB version, not the regular 512MB one. i'm currently posting my 2900xt for sale on anandtech's forum since i didn't think it was possible to crossfire the 2900xt with the 3870. please let me know or pm me. Thanks alot.

[Super Nade]

dng, did you try XFiring it before? Maybe you can poke around a bit and let us know how it goes?

[dng]

i have not, but i will definitely give a go. i still need to get a crossfire board. i'm waiting on the 2900xt from sapphire as they're sending me a replacement. i was hoping that they would send me a 3870 since this 2900xt is pretty rare. too bad they're replacing it with an exact 2900xt. i hope it'll be painless and i'll gain some performance. i will post back once i get everything in place. i googled and got some infos on how to crossfire the 2900xt with a 3870.

[AliG]

The r600 and the 3870 are basically the case card though, just a die shrink, the r700 cards have architectural tweaks that will probably make it unlikely for xfire to work

[dng]

off the bat, i know the memory bus is different, 512bit(2900xt) vs. 256bit(3870). the process is different as well 80nm vs. 55nm, i think. the only thing that i'm a bit skeptical of in getting crossfire when the difference in memory. the 2900xt has 1GB of ddr4, but the 3870 only has 512MB. it's promising that i see some people got crossfire to work with a 2900xt and a 3870. the drawback might be having the 2900xt acting as a primary gpu and the 3870 as a secondary. i got to order a 790fx board now.

[Giacomo]

All this is very interesting.

Zanzabar, can you tell us how did you crossfire the 3870 with the 2900?

Giacomo

[zanzabar]

zanzabar:

how do you crossfire a 2900xt with a 3870? i love to know how as i have a 3870 and a 2900xt. please note that the 2900xt is the 1GB version, not the regular 512MB one. i'm currently posting my 2900xt for sale on anandtech's forum since i didn't think it was possible to crossfire the 2900xt with the 3870. please let me know or pm me. Thanks alot.

i had the 3870 512MB sapphire and a sapphire 1GB 2900xt i just plugged in the bridge and installed 7.12 or 7.11 and it worked but it wasnt my 2900 so i couldent keep it

[AliG]

off the bat, i know the memory bus is different, 512bit(2900xt) vs. 256bit(3870). the process is different as well 80nm vs. 55nm, i think. the only thing that i'm a bit skeptical of in getting crossfire when the difference in memory. the 2900xt has 1GB of ddr4, but the 3870 only has 512MB. it's promising that i see some people got crossfire to work with a 2900xt and a 3870. the drawback might be having the 2900xt acting as a primary gpu and the 3870 as a secondary. i got to order a 790fx board now.

But the point is that there weren't any architectural changes, ati simply just simplified the mem bus to get to 256 from 512. The rv770 on the other hand shifts from a 4:1 to 3:1 alu:text ratio, has more shaders and there's supposed to be a difference in shader+core clocks. So even if you could xfire them the game play wouldn't be as smooth due to the microstuttering of the 3870 lagging behind (especialy with af due to the extremely low texture fill rate) as the cards would rendering the game at different rates (that's one reason why I find hybrid xfire and sli a waste).

[Mungri]

It would be awesome if they can be crossfired. We'll have to wait and see, but I dont think it will work.

[dng]

hang in there, i got the dfi 790fx board coming. i will post back once i get it running. i think the trick is to find the right driver version that allows hybrid crossfire. i have a bunch of old drivers as well as the new 8.4. i have no luck selling my 2900xt, oh well. this should be fun and hopefully painless to do.

[Toritechie]

I've been searching for information about the pairing of a 48xx and 38xx series in crossfire ...

NOTHING ... nobody has posted anything that indicates it can be done, and how well it can be done.

Surely, someone out there has tried this allready. I'm running 2 3870's in crossfire on a board with 3 PCI slots, I'd love to know if I'll have a working system - and an improved one - by adding in a 4870 to the array.

Please post if you've any helpful information/testing.

[Heretic]

They're working on 4-series cross compatibility, but mixing 3 and 4-series won't work and no one is officially working on it.
http://www.fudzilla.com/index.php?op...=8075&Itemid=1

[AliG]

HA! I was right, see zanzabar just because they are in the HD family means nothing. Its the series families that can be xfired. Ohh well either way I still bought a 4850 and it will be a massive improvement over my 6600gt regardless and I only paid $150 after 2 rebates! WOO HOO! Its a shame I can't xfire the card due to my nvidia mobo

[HeX_00]

HA! I was right, see zanzabar just because they are in the HD family means nothing. Its the series families that can be xfired. Ohh well either way I still bought a 4850 and it will be a massive improvement over my 6600gt regardless and I only paid $150 after 2 rebates! WOO HOO! Its a shame I can't xfire the card due to my nvidia mobo

Wouldn't write it off just yet...

http://www.tgdaily.com/content/view/38056/135/

http://www.forumdeluxx.de/forum/show...&postcount=712

[Heretic]

I would. http://www.fudzilla.com/index.php?op...=8075&Itemid=1

[HeX_00]

I would. http://www.fudzilla.com/index.php?op...=8075&Itemid=1

That was posted the exact same day tgdaily posted their article saying that it was possible.

So I maintain, don't write it off just yet.