On the upside, the new motherboard can handle a Crossfire - the older one could not.
You'll see very little increase in the benchmark because you'll just be more CPU-Bound.
I should clarify the 'Feeding a monster' analogue to best illustrate why:
Your CPU feeds your GPU with just a few bowls, which have to be emptied before they can be filled fresh again. There are some fun details about VSync and Triple Buffering that this analogue is also used to explain, but I digress.
Your GPU is damned hungry, but it can only eat so fast. If you put a small bowl in front of it, it empties it in half the time of a bowl twice the size. Resolution is your bowl: It takes even a monster GPU a little longer to empty a large bowl than a small one.
SLI/Crossfire is like having two mouths to feed, but they have to eat from the same bowl. They empty bowls comparatively faster, but refilling those bowls then becomes a problem. This is why SLI/Crossfire only sees performance gains at large resolutions: Bigger bowls to eat.
Your CPU has a pump to fill the bowls. It can pump a given amount of food with other factors like memory and PCIe bandwidth being like the size of the nozzle. The pump is run off the same engine as other stuff like Physics though, so it can be starved for power at times. The CPU can be filling one bowl while the GPU is eating another, but there's still time involved for the CPU to grab and 'wash' and fill another bowl.
The bowls are simply frames. Bowls eaten being frames per second.
When you go to SLI/Crossfire you have two, three, or even four cards eating from the same bowl
. Most people think this would double the number of bowls eaten, but their CPU can't pump that much. The cards are starving for more, especially when the bowls are too small, because the CPU doesn't have time to clean and fill even one bowl before they ask for another. When you run a larger resolution then, the CPU spends less time 'washing dishes' and more time filling the larger bowl.
At any rate, the thread title is misleading: Your processor is the problem if your resolution is too low
, and the benchmarks run a hilariously low resolution on some settings. Edited, Sep 12th 2013 3:58pm by Raelix