I have FCP 7 and have noticed it will "red line" (requires render) for relatively simple things. Here is a common scenario:

Editing corporate video project, 30 mins+ single footage file from EX1, transcoded via XDCam Transfer. I will edit the footage together with powerpoint slides, created by saving each slide as a PNG from Powerpoint (large slides, whatever the max is. . .3000x2250 or something because I will sometimes "zoom in" on the slides). Since the slides are almost never widescreen and the project is, I will put a layer under each slide with a solid color (FCP video generator effect) that matches the overall background of the slide. I realize I could do this in photoshop and essentially make the slides widescreen but I don't know how to do that QUICKLY.)

Sometimes color correct the footage but have this issue even with no FX on footage.

So basically, a sequence will usually START with the bright green lines (need render but can preview in real time) but shortly thereafter will start redlining all the time. Trying to track this down to system inadequacy, needing more RAM, or needing to change FCP 's RAM-related settings.

I have a 2011 Imac maxed out (except for RAM, have the stock 8 GB out of possible 16--I think). Running Mountain Lion if that matters.

Wondering if anyone can enlighten me?

I had this too and I think I ended up making all the stills into a format identical to the timeline by using make freeze frame as I also found that the PNG files were causing the system to crash and constantly run out of memory.

That makes sense. Is the freeze frame same res as timeline settings? That would make it look kinda crappy when zooming. Other than that sounds brilliant

That makes sense. Is the freeze frame same res as timeline settings? That would make it look kinda crappy when zooming. Other than that sounds brilliant

Well you could zoom it first and then make the freeze frame, this was a few years ago so I can;t be sure that is what I did but I certainly know that just putting stills on the timeline seemed to cause me problems.

intriguing. I've just been doing it for so long without question. Now I know, and knowing is half the battle.

G.I .JOSH!!!!!!!!!

I used to get the run out of memory flag a lot and it took me ages to figure that it was that I was using still images and I think it was just filling up the buffer with crap.

Toggling RT and Safe memory playback cleared it for a while and then it would flag up again when I made the stills into a different format it went away.

What format do you mean? I use PNGs on recommendation of client (also an editor) that I'm editing for.

Try TIFFS or JPEGS. As long as you don't go beyond the pixel size limit, they should work well.

I'm assuming smaller file size = better performance? i.e. JPEGS over TIFFS. except for compression artifacts. Not sure why the PNGs were used in the first place. . .just following orders.