PP CC Running Very Slow Once Clips Assembled

Question

Here is a description of my problem, any guidance would be greatly appriciated.
I imported about 20 GB of 1024p, 24fps video from a Canon T3i, and about 1 GB of Audio from an H4N zoom mic for my current project. Everything ran smoothly when I was naming clips and synching audio. But once I chose the clips I wanted, and assembled them into scenes on the timeline (I'm making a 5 minute short with 6 scenes), playback became extreemly slow, and now it has now come to a virtual stop, as when I start the program, 5 minutes later, I still have a black project viewer.
I have had a similar problem with another project that had an hour of footage (from one clip) cut down to about 3 minutes.
My System:
Mac OS X 10.8 (dual-booted, running Mac)
3.1 Ghz Intel Core i5
4GB 1333 Mhz DDR3 Ram (expandable to 16GB)
AMD Radeon HD 6970M 1024 MB
1TB SATA Hardrive (Partitioned; Mac: 702 GB total, 120 GB free / Windows: 297 GB total, 235 GB free)
I suspect the problem might be my small ammount of RAM, but I wanted to check with some people online before I jumped and expanded my ram.  Or I also suspect that the problem might be the free storage space / total space ratio might be a little low on my Mac Partition (120 / 702).  As I said before, any guidance would be greatly appriciated.  Thanks.

Answer 1

Your processor is fine.  True, I would not build a system with less than i7 with 4-core/8-threads, but it seems the biggest bottleneck in your case is your lack of hard drive separation (but even that shouldn't cause the issue you've described).  Many will advocate all kinds of crazy hard drive configurations, but at the miniumum, when money is tight, you should have:
HDD1 (7200rpm or faster) running: System (Mac and Windows), Project Files
HDD2 (7200rpm or faster) running:  All Media Files (audio and video as well as rendered temp files, conform files, disk cache, etc)
So the very next thing I would purchase, in your situation, is an external 7200rpm drive with the fastest interface you can get (USB 3.0 or Thunderbolt).  Make SURE it's 7200rpm, mfgs like WD don't really tell you what's inside the casing.  I personally like external hard drive docks best.  The docks aren't so expensive, and the drives are much less expensive.  Plus you know exactly what drive you're getting when you purchase an "internal" drive and place it in your external dock.  Make sure to get a second drive for backing up your footage and projects.
Some will argue that 4GB of RAM is a huge bottleneck, and they're right.  Just keep in mind that Windows users like myself only get 4GB of performance (even in a 32GB system) when dealing with most Quicktime files (such as the T3i).  4GB RAM kind of sucks on big projects, but it's much more bearable than editing on your system drive.  Also, most of us were editing 5D mkII footage on dual-core systems well before the i5 came along (dual or quad).
One final thing:  Do you have hardware acceleration turned on?  The problem you describe doesn't sound right at all.  Also, do you have any Warp Stabilization applied to any/many clips?