8GB RAM or 16GB RAM?

School of Motion wrote a blog post about building the Ultimate After Effects computer a few years back.  They spoke to Adobe product managers and engineers:

https://www.schoolofmotion.com/blog/after-effects-computer

In a nutshell, they concluded:

• Higher CPU speeds are better than more cores for After Effects
• It’s best to have a high-capacity RAM and GPU. More is better.
• After Effects doesn’t use multiple GPUs. A single GPU with high vRAM is the goal.
• Memory (RAM) cache is always faster than disk cache
• There isn’t a clear winner to the AMD vs NVIDIA debate for GPUs.
• It really matters that your GPU drivers are up to date. (Editor's Note: Mac drivers are updated with iOS updates)

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@mel5E6D wrote:

not sure if the RAM amount would make a big difference in previews? I don't mind long rendering times, but what is important to me is if I can rewatch my clip without it lagging. 

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More RAM won’t make much difference in how fast the frames render, but more RAM will make a difference in how many rendered frames can be held in RAM for a RAM preview. The more RAM you have, the longer the RAM preview can be.

Because you want a lag-free preview, you want a RAM preview, because it’s the fastest kind of preview to display. Nothing is available faster than reading the contents of RAM. Therefore, to take advantage of RAM previews in After Effects, get as much RAM as you can afford. My aging laptop is maxed out at 16GB RAM, but I would have gotten 32GB if that option was available at the time.

What happens if you don’t have enough RAM? The maximum RAM preview (in seconds) becomes shorter, and if it’s shorter than your composition, then when you run out of RAM for rendered preview frames, the rest of the frames in the composition RAM have to either be rendered on the fly, or read from the Media Cache…and both of those are slower than a RAM preview. They are laggier.

If you don’t have enough RAM for the length of RAM previews you need, your previews will be more dependent on the speed of your CPU (to render the previews on the fly) and the speed and capacity of the storage where you keep the Media Cache (for pulling cached renders from storage). If your budget is so low that you also skimped on CPU and storage speed/capacity, just don’t expect high performance. Good After Effects performance depends on a budget big enough so that CPU speed, RAM capacity, and storage speed/capacity will not bottleneck the other components. They work together.

Another way to look at that is if you don’t have enough money for 16GB RAM, do not also short yourself on the amount of fast storage, otherwise the system will be cornered when it tries to cache what won’t fit in RAM. The data will have nowhere to go, therefore, lag.

If you need more info on how After Effects previews work and how RAM is involved, this article might help:

https://screenlight.tv/blog/the-definitive-guide-to-ram-previews-and-disk-caches-in-after-effects-ie-those-blue-and-green-lines

After Effects is a hungry of RAM memory so in fact the least you should have is 16GB, you have the effort and put those 16gb and a solid disk of at least 512GB so you can also use the disc cache together with the RAM, with this and a decent processor (the current ones are) you can work at least for a time that you can afford a much more robust PC.