1 Reply Latest reply on Jul 4, 2010 9:19 PM by Todd_Kopriva

    question regarding RAM & multiprocessing




      Been rendering out my HD comps and running into a small problem with AECS5.  I have a core i7 iMac w/ 8GB RAM.  My comps are crazy complex, lots of 3D, shadows, motion blur and large image files with alpha channels (3600 x 3000 pixels).  Everything my grandmother told me never to do.


      I've pulled back as far as I can go on the settings, going any further and the client grumbles, so my hands are tied.


      I can render everything fine by setting the RAM allocation per core to 3GBs.  My poopoo is that this kills multi-CPU rendering on my machine, even though I have 8GBs installed.  Why can't AE use two cores?  I was never a wiz in math, but 2 x 3 was 6 last time I checked...


      So here I am, watching the Activity Monitor window on my machine while AE only chews on 40 ~ 50% of my CPU (heck, the fan doesn't even whir).  I've made an online purchase for 16GBs of RAM and am hoping this will provide AE, and in consequence the CPU, with enough data to keep it busy.


      Oops, forgot to ask my question... How many cores, or CPUs, or whatever, can I get going on a machine with 16GBs of RAM while allocating 3GBs per core?  Of course, I'll max out the RAM pool all the way.  At the moment, AE won't let me allocate more than 6.5GBs of 8GBs to AE & friends.




      Oh!  And happy independence day! 

        • 1. Re: question regarding RAM & multiprocessing
          Todd_Kopriva Level 8

          The math works this way:


          With 8GB in the machine, After Effects CS5 keeps 2GB for other software. This is a good thing.


          That leaves 6GB for After Effects. The foreground application (the instance that holds frames for RAM preview) gets 1.2x as much as allocated for each background process. So, if you have 3GB allocated per background process, the foreground process takes 3.6GB. That leaves 2.4GB for background processes, which isn't enough for even one to start. So they don't even bother, and the foreground process is left to do the rendering.


          Let's take another example, just to make it clear: My computer has 24GB of RAM. If I'm working with digital cinema frames, I allocate 3GB for background processes. I also leave 4GB and 2 CPUs for other applications. So, After Effects gets 20GB. The foreground process takes 3.6GB, leaving 16.4GB for background processes. That's enough for 5 background rendering processes. That works out nicely, since (with the one foreground process) that keeps 6 of the 8 processor cores in my machine busy with After Effects.


          More information here: