SLI and Cross Fire

[STMahlberg]

+1 to #2...

The only caveat is that if you are are running two 5970s in the same box without a super high-end motherboard, you HAVE to run Crossfire to get them to work at all. Learned this one the hard way...

Why was that?

I have a theory about this since my discussion with Maxwell on this topic... Keep in mind it's only a theory.

From what I have read my understanding is that the 5970 is basically two processors on one card; my first theory is that when running (2) 5970 on one board that his may confuse (for lack of a better term) the CPU into thinking that there are 4 cards running in only (2) slots and it doesn't know what to do with what appears to be redundant information.

The second theory is that on many low end motherboards, eventhough they have 2 or more PCI-E slots on them, not all of the slots run at the same speed they may be operating in x16, x8, x4 or x1 modes.

Now this all may make complete sense except for one thing... I just made all of that up. Sounded pretty good though, right?

I made it all up except the last part and half of the first part.



Seriously though... I don't know what kind of motherboard that Maxwell has but it may have something to do with the PCI-E modes. I bought a MSI 890FXA-GD70 and if you look at the specs eventhough it has (5) PCI Express 2.0 x16 slots, they run in different modes: (2) x16, (2) x8, (1) x4.

I was looking for a new motherboard for my two 4850's when I noticed this issue.