I'm curious what kind of footage you're using at 50 MB/s.
All NLEs require a RAM buffer in order to stream video (and audio) at a constant rate.
You could try some experiments with different RAM values in the Preferences.
But, I see the same thing you do, I think. I can shuttle/scrub sequences and even single clips in QT Player, Avid, FCP, etc., and it's smooth as silk. But, bringing them into Pr (also on Mac), it's an entirely different story. Lots of lag. Lots of dropped frames, both in the Source viewer, and in a matched settings Sequence with no effects or changes of any kind.
It's one of my few peeves about Pr.
My guess that this is due to the architecture Adobe chose when they decided to focus on native editing. All media is probably going through some process, even when it doesn't need it, such as when using intraframe sources.
Oddly enough, I get better/faster scrubbing with Long-GOP material than ProRes intraframe, even though I would expect it to be much worse. There's more data being shuttled normally with intraframe, and perhaps the buffers built into Pr just aren't as large as they should be. Or, perhaps the order of decode and load into RAM buffer is opposite of what it should be.
You can adjust the audio buffer in the prefs. Maybe what we need is an adjustable video buffer as well. Or, maybe Adobe could include some code that makes it larger when it detects as much RAM as you have.
Maybe somebody with more engineering know-how can offer some insight.
"I can shuttle/scrub sequences and even single clips in QT Player, Avid, FCP, etc., and it's smooth as silk. But, bringing them into Pr (also on Mac), it's an entirely different story. Lots of lag. Lots of dropped frames, both in the Source viewer, and in a matched settings Sequence with no effects or changes of any kind."
That's about the most depressing review anyone could offer of an NLE, since it involves virtually every T-L and editing operation.
Are folks experiencing much the same thing on PC platforms w/CS6?
Okay, wernt back and looked again, 50 MB's was the peak transfer not the average, well spotted! those are ProRes 422 files transcoded for FCPX and the average read was 16 MB/s.
I have to eat some humble pie here because I tried bringing the transcoded files from FCPX into Premiere and it handled them in much the same way as FCPX, ie as a steady data read from the drives. When premiere reads the native C300 files is when it handles the data loading in a different way resulting in the less steady data stream.
I really don't want to go back to transcoding everything to ProRes, but maybe that's the best way to stop premiere from locking up.
CS6 does have issues with some native formats, especially on longer takes, that exhibit the behavior you've described. Adobe is aware of the issue and working on a fix.
Until that patch is released, ProRes may be the better alternative.