Mixing memory

[Luke]

Hi all, I'm doing the unthinkable, and mixing memory types.
The MB is an MSI P35 Neo2-FR.

Slot 1: 1024mb OCZ Special Ops PC5300 4,4,4,12 - 1.9v
Slot 2: 1024mb OCZ Special Ops PC5300 4,4,4,12 - 1.9v

Slot 3: 1024mb Corsair XMS2 PC6400 5,5,5,15 - 1.9v
Slot 3: 1024mb Corsair XMS2 PC6400 5,5,5,15 - 1.9v

Aside from ditching one lot and starting again with matched memory (which I accept I may have to do), what is the best way of me configuring this in the bios to get the best out of it (or even just let them run together)?

Cheers

 

[Luke]

So in reality, what is quicker?
faster clock, or tighter timings?

1024mb OCZ Special Ops PC5300 4,4,4,12 - 1.9v
1024mb Corsair XMS2 PC6400 5,5,5,15 - 1.9v