View Full Version : CS5 Memory & Multiprocessing

05 May 2010, 06:35 PM
Greetings all,

I am playing around with the "Memory & Multiprocessing" settings in CS5 and I am trying to allocate RAM for "Render Multiple Frames Simultaneously" (RMFS). Unfortunately, the math just isn't adding up, and I want to make sense of it.

My workstation has dual quad core processors and 8GB of RAM. The default settings are:

Installed RAM: 8GB
RAM reserved for other applications: 1.5GB
RAM available for AE (and other Adobe applications): 6.5GB

Installed CPUs (processor cores): 16
CPUs reserved for other applications : 2
RAM allocation per background CPU: 2GB
Actual CPUs that will be used: 2

*Note: The "Actual CPUs that will be used" settings changes automatically if you change other settings.

So according to my research on these sites (among others):

...I have 6.5 GB available to AE (no other Adobe Software running), so if I allocate 2GB per background CPU, I should have at least a "3" in the "Actual CPUs that will be used" slot, but it only shows a "2."

If I change the "RAM reserved for other applications" to 2GB, the "Actual CPUs that will be used" drops to "0" even though I have 6 GB "RAM available for AE".

What gives? Why doesn't the math add up?

06 June 2010, 07:42 AM
I'm struggling with that, too. Unfortunatly I haven't found any real informations about it. Any insights are welcome.

06 June 2010, 05:24 PM
When you have 6.5GB left for After Effects, and you allocate 2GB per process, that gives enough RAM for three processes. One of those is the foreground process. That leaves enough RAM for two background processes.

When After Effects reports that 2 CPUs will be used for rendering, it's telling you how many background processes will be rendering simultaneously.

When background processes are rendering multiple frames simultaneously, the foreground process doesn't render but instead coordinates things and holds the RAM preview frames.

The reason that the number goes to 0 when you leave 2GB for other applications is that After Effects CS5 allocates to the foreground process 1.2x the RAM that the background processes each get. So, if you leave 6GB for After Effects and say that 2GB is how much RAM background processes need, then the foreground process takes 2.4GB first. So, you're down to 3.6 GB left, which is enough for 1 background process. But there's no point in sending rendering to the background processes if there's only one of them. So After Effects just uses the foreground process.

I'm about to write a set of blog posts about CS5 like the ones that I wrote for CS4 (which you pointed to in your original post), to clear up these details.

06 June 2010, 11:49 AM
That clears it up. Thank you very much for your explanation. I really appreciate it.

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06 June 2010, 11:49 AM
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