the "bit" in this case is the application binary and has nothing to do with image "bits".
Oh right, DOH! Jeeze, that really was dumb.
But Jeff, in a previous thread you posted "But if you are opening Camera Raw hosted in Bridge (command/control R) vs Photoshop (command/control O) then you are opening the 32-bit version of Camera Raw, not the 64-bit version. Depending on your Bridge prefs, double-clicking may open ACR hosted in Bridge or in Photoshop. You really, really do want to be sure you open ACR via Photoshop that is running as a 64-bit app, not a 32-bit app." http://www.luminous-landscape.com/forum/index.php?topic=45590.0
Why is that, is it a refresh speed issue (the topic of the earlier thread) or something else?