It's been several years since I've been to a Networkers conference, but there used to be a Cisco presenter who perennially delivered a presentation that dove into just what you are asking. I remember him going into process switching, fast switching, CEF, line card differences, hardware vs software-based processes, etc.
If you have any colleagues with access to previous years' Networkers presentations, you might scour that source. Sorry this answer doesn't help a lot right this moment, but do consider Networkers (aka Cisco Live!) in the coming year. It is really an invaluable source of inside Cisco training "not available in stores".
