If you wanted to do it up to the max you could do a total of 24 gigs by installing 4 gigs sticks of RAM using the first 3 slots of each riser card and leave the 4th slot empty. That will give you the best combination of maximum RAM and maximum memory bandwidth.
Remember that a current generation MacPro has two riser boards for RAM, each with 4 slots. The first three slots of each board are interleaved. The maximum size of RAM you can get right now is a 4 gig stick. So by using 6 - 4 gig sticks, populating each of the first 3 slots of each riser board you get your 24 gigs total. The MacPro, running in 64 bit mode, will recognize this by default when you startup.
Smoke, also running in 64 bit mode, will address this RAM. For example, this can be beneficial when loading high bit depth and/or high resolution images in Action when compositing.
Now whether the additional expense of doubling your RAM from 12 to 24 gigs is worth it is entirely up to you and the projects you may be working on. I really don’t have any bench marks to help you in that regard. You might want to contact your local Autodesk Smoke dealer and see if they have a similar setup for advice.
Thanks Paul, for the detailed answer to my questions.
Yes the imagery that i might be using maybe pretty high res, but i was more interested in finding out if more ram can be beneficial in terms interactivity with lots of layers in action (while moving layers around using transformations in axis, color correction etc).
and yes, you guessed my name right :)
2012 SAP2 SP3
Kona 3G driver 10.3.2
Quadro 4000 driver 256.01.00f03
Cuda driver 4.2.10
Mac Pro (mid 2010)
12 Cores / 24 Gigs
CalDigit HD Pro2 (8TB, 723 MB/sec read)