ATI Crossfire X / Nvidea SLI

As the topic title suggests, just out of curiosity while i think of it, i have no idea what does / doesn’t like Crossfire X / SLI, however i do know that some games struggle with it.

I was just wondering if you’d thought about overcoming any problems with crossfire / SLI, or better still any of your BETA testers use either / or.

Only querying since i have an ATI 4870 x2, getting on a bit now, could do with upgrading really, but funds say otherwise, so it’s here to stay for now, but in order to play this game will it be crossfire / SLI friendly? as a 4870 x2 is 2 GPU cores on one card, therefore cannot disable crossfire.

Thought i’d get this query in ASAP incase it involves any extra coding? No idea, i’ll leave the technicals to you guys :blush: I can build / modify / overclock computers successfully and thats about it. :blush:

Any reassurance this game, when released will be accepted by my, and many others hardware would be much appreciated.

well basically there are only a couple of ways SLI/crossfire could increase the framerate (from a technical standpoint).

a) GPU 1 works out the odd pixels (1; 3; 5; etc.) GPU 2 the straight ones (2; 4; 6 etc.)

b) GPU 1 does the upper half of each frame; 2 the lower half

c) GPU 1 and 2 work like in a), but with complete frames instead of pixels.

SLI and Crossfire both use version c) afaik

since only a handful of the other beta testers posted their specs in the thread in our hidden subforum (and the devs rightly didnt do it for them) i cant even tell you if someone there has a similar setup. Those that posted dont have multigpu cards.

I could be naive on this and things have changed, but I do not believe we as game developers have to do anything special to take advantage of crossfire.

SLI on the other hand, does.

I could be very wrong about this, my google-fu doesn’t seem to be good on this one.

After a bit of googling i’ve found it appears to be more of an ATI driver problem when it comes to OpenGL games.

I’m currently running driver vers 11.3 so to test tried Cities in Motion, the game mentioned at the top of that link, and the game wouldn’t load, however using the .dll from the older driver suite and it does. So it seems it’s more of an ATI issue than specific games supporting / not supporting crossfire, however i don’t know about SLI. If automation isn’t running on OpenGL i should have no issues, however if it is, and i do, i should be able to fix it using the above .dll with any luck, i wonder what ATI are doing to fix the issue, if anything seeing as they keep releasing drivers which have the same OpenGL preblems. :confused:

Thanks for the replies, and explination Deus ex Machina, i knew that both cards split the work load rather than just rendering the same thing together, just didn’t quite know how :stuck_out_tongue:

All DirectX - so should be all good in theory

unless u try to port it to a non M$ system of course…