Playback issue

The playback in the timeline is pretty choppy, or at least not smooth.
When I press the space bar to stop the play back, the cursor doesn't stop right away and jumps a couple frames ahead.
So of course I can not edit in these conditions.
I played around with the playback options RT/Dynamic.... but nothing makes a difference (unless I set it wrong... dynamic is the best for playback right?)
I am working off of avi files captured off my crappy camera.
What else....
Oh, no graphics or animation or multi layers of video...
My system is a Powermac G4 dual / 512mb.

Thanks for helping.

Sounds like a laggy system. Why are you working in AVI? Why not capture straight from your camera into your mac via firewire? Are you running a firewire external disk?

The camera is an older camera and doesn't have a firewire cable
And yes, I am using an external HD... this might be the problem. To hard to access the data for the G4. I'll do a test with the media on the HD.

I've never actually edited on final cut off a G4- they were laggy, last time i tried. The fact that you don't have that much RAM (512mbs) and the processor isn't very fast for media, makes lagging likelier, especially if the processor has to carry the load of an external hard disk as well.

You're going to have to keep the system light, if you want to edit off it- simple codecs, short projects, not so large a hard disk, properly configured system, etc...

but some of the other guys who have worked on a similar setup may have better suggestions.