RAM preview is not beeing cached – sometimes

Question

Hi,
I read through the Adobe recommondations for multiprocessing, I hope I did not miss a crucial point, but here's my problem:
When multiprocessing for RAM preview is activated, it renders the required frames and plays them as expected. Also the area in the timeline appears green as expected. But in the moment I click somewhere, the part of the timeline goes gray again. When I want to see that part again, I have to start the render for that part all over again – it feels like it was not cached at all. When MP is deactivated, it works as expected – but unfornutaley, my comps benefit a lot from MP and the render goes a lot faster so its really slowing me down to deactivate it. Parts that are cached without MP stay in cache when they are in a part that I re-render with MP later. Then just the new MP rendered parts dissappear.
Because this behavior just started at some point my opinion was that its kind of a bug. I purged all memory and cache. I uninstalled AE with this clean uninstall tool from Adobe and reinstalled.
It just happens in some complex comps. So I thought, it might be some option or something that prevents AE from caching mit MP. In one composition, I just have one comp with time remap. When I made a new comp and copy'n'pasted the keyframes, it worked in that manually cloned comp.
Disabling disk cache does not seem to have any influence on the problem.
It's strange and hard to reproduce and I was not really able to boil down the conditions where it happens for sure. Any hint what might be the problem would be very appreciated.
Thanks in advance,
Timur
My system configuration is the following:
MacBook Pro i7 2.3 GHz, 16GB RAM, 256GB SSD, nVidia GeForce GT 650M
Mac OS 10.8.4
After Effects CC – 12.0.0.404

Answer 1

Thanks for that reply! Any thanks for the insights in your workflow, I am always curios how people master that stuff. Its just that in the project I am working in the moment I notice a dramatic increased performance using MP and was kind of dissappointed when it just stopped working at some point. I was hoping to save time in the bottom line solving the whatever problem this is (too late now, still I want to have it solved). It bothers me that it's not working and just feels wrong how it behaves...
Now to the specific problem:
Well, first I thought "cpu's used for other applications: 0" would not have that much effects, since its just using 3 CPU anyway because of ram limitations. But ok, changed it to 4 and the memory per CPU to 1, so its using four CPU's; an even number, did not change anything.
I do not use any plugins . Or let's say: not that I know. I use AE of the box and freshly (2 weeks ago) installed.
Yes, MP turned off is the way I am working right now but I did not really consider this a resolution. I am also aware of the fact that MP is not faster in all scenarios, but is in mine now. And yes, I also read that MP causes problem sometimes, but I rarely read about unsolvable ones. Why support it in the first place if it would be so? I wouldnt understand if there are usefull features implemented in expensive software my company payed for that are broken, thats all . Or, if there's a bug I would like to help to solve it so it gets more usable.
Again, thanks in advance for further help, looking forward to find the solution!