IMovie 08's realtime performance scales to H/W spec?

Question

There's been ongoing discussion of whether iMovie's output quality is limited by single field processing and 960x540 canvas size. While many have experienced decreased resolution detail of HD output, Winston has shown an example of full HD output, which is an uplifting news.
Now I conducted a simple experiment to see if this single field processing is true.
I created a 1440x1080 image in photoshop with blue and red stripes alternating, half vertical and half horizontal (top image). I exported this image from Quicktime player to 1440x1080i AIC quicktime movie to bring it into iMovie 08 (second image). Vertical part has been smeared into purple color, a result of AIC's chroma subsampling. You can still see the hint of vertical stripes.
In iMovie's project, the image looks half red and half purple, as does the output Quicktime(third image). If iMovie reduce size in half without discarding one field it would've been flat purple. The fact that it is flat red indicates that iMovie ignores one field for processing and outputting.
I've been trying to reproduce Winston's full quality HD output but no luck so far. I believe I used the same procedure as his, and the only difference is the hardware spec.
Winston, your signature says that you use Quad core Mac pro with 3GHz speed and 4GB ram, where mine is a mere Mac mini with core duo processor and 1GB ram. Obviously the two has big difference in GPU power and graphics memory. I think a possible explanation for your full HD output may be the top of the line system spec. If iMovie is capable of optimizing its performance to the hardware it's running on, maybe iMovie processes movies in 1920x1080 canvas instead of 960x540 size.
I think this is pretty cool thing if it's true. Apple still need to add an option for outputting movie with software only processing (and no GPU) for maximum quality on low end machines, but at least this performance scaling makes iMovie more intereseting tool for highend mac users.

Answer 1

Euising
I note your points about processors and this could well be the case. I noted that it takes about real time or less to import AVCHD to AIC through imovie (really rough estimate as I've never actually timed it, indeed I've never actually thought about it) but it seems to take about 4 or 5 times as long when I import to the same AIC quality using voltaic, perhaps voltaic can't utilise my CPUs as imovie can.
Back to the issue of tests, I made a 1920 x 1080 test slide in photoshop which I saved as an interlaced .png
This is a screenshot of that file, most lines are of a single pixel width and I've tried to utilise the primary RGB and CYMK colours.
I opened this file in QT and exported to AVC 1920 x 1080 interlaced
This is a screenshot of the export. Disappointingly the export wasn't quite the same as the original as you can see. I've got some thoughts about why this occurred but since exporting PS projects to AVC in QT isn't what we are discussing I'll let that lie.
The final step was to import the movie file to imovie and export it as AVC 1920 x 1080 interlaced.
I'm sure you'll agree it's identical to the file I imported into imovie. I did diverge from your workflow a little because I wasn't entirely happy I knew how the anamorphic nature of AIC would affect my results.
I've posted the original movie file here should you wish to put it through imovie yourself for comparison, I'm going to try to fit in doing the same thing on my laptop to see if I get a different result. (I think the web page may well be blank if you use the link, but you should be able to click and drag the blank webpage to your desktop to download the file)