On a recent project (see my last post) I ran into a situation where Logic Pro was literally stumbling and halting quite frequently giving me the standard (and far from helpful) “Logic is too slow error”.

However, I noticed that if I stopped and started it from the same spot many, many times it eventually played through just fine. How weird!

After much testing, I figured out what I believe the cause of this. This recent project had the following attributes to it:

1. I was running on my Power Mac G5/2×1.8 Ghz with 2 GB RAM
2. Most recent version of Logic Pro and Mac OS X 10.4.x
3. The project had some very long “songs” which were film scores, ranging anywhere from 5-15+ minutes per “song”. (I have multiple “songs” that then made up the entire project
4. The cues were all written in a classic “star trek” style, utilizing full orchestral sounds, though with sparse orchestration. Hence, I might have 40-60 exs24 instruments loaded up (many of them keyswitched samples from the likes of libraries like Vienna Symphonic Library (vsl) and Project SAM True Strike, etc.) so there was a significant amount of samples at my disposal.
5. exs24 streams samples from disk, but also requires a certain amount of RAM per exs24 instrument (around 8-14 MB, depending on settings and such)
6. I was using very limited “plug-ins” besides a reverb or two which was being powered off of a UAD-1 card (almost zero CPU hit) and was streaming the samples from a separted SATA RAID HDD, so bandwidth on that end should not be a problem

What I discovered in the end was that I simply did not have enough RAM to run these projects I was loading effeciently. I watched the RAM counter (using the unix ‘top’ command) as I fired up one of these songs. Before loading the song, I had about 1.2 GB of free physical RAM. As the instruments loaded, that number continued to shrink until I hit about 32 MB of RAM. At that point, the instruments continued to load and load and load, but presumably were being shuffled around by Mac OS X in virtual memory.

This then explains why at first the song would stumble, and then after multiple tries, it would work. The reasoning I figured out was that even though all those instruments were loaded for the SONG, for a particular cue, I may only be using a fraction of those instruments at the same TIME. So, the system had to arrive at the sample it needed, freak out and stop because that samples was in virtual memory, swap it into real RAM for the next attempt, and so forth.

Needless to say, I have 1 GB additional RAM on order now and will even push it to 4 GB if needed to get the performance back!

Hope this quick articles saves someone the headache that I went through!

John Blog Post, Logic Pro, Tips and Tricks