doni,

They do seem to be 3 distinct items...

With that, they claim "inventions in caching" where the question is then either an innovation using the flash as a cache as initially stated, or, caching, as in I/O in front of the flash as e.Digital does.

Two different issues....

I agree with you here from the same page I cited...Because ReadyBoost stores its cache as a file rather than directly using the flash device in a raw manner, that file system must be mounted and assigned a drive letter. Simply mounting a subfolder of another drive won't suffice because only the root folder of a drive is suited for ReadyBoost cache — otherwise the “ReadyBoost” tab will not appear in the logical volume properties, nor will any previously created cache file be used.

seems this too may be the differentiator.

g