Assuming that a user sets up a PMI (or LiveCD), is there any point in setting up a cache partition?

I understand what a cache partition is and does, but if you are running off of a compressed OS, rather than a full HD install, does the OS even "know" whether or not you have reserved a cache partition on any hard drive, and will it be able to find it? Is there a setting or cheatcode where you can "tell" the OS that the cache partition exists or where to find it? If not, and someone sets up partitions for a PMI (or LiveCD), and includes a cache partition, will the OS find and use it, or are they just wasting time and HD space?

I have to admit, I've been running a PMI with a cache partition for about a year and a half (left over from an earlier failed HD install), and it recently occurred to me that I have no idea on Earth whether it even works in this context!!

This leads me to a second related question. Partitioning can be risky, and it can take a lot of guts for a Linux newbie to risk a working Windows installation to partition a HD for use with a Linux option. Is there any file-based cache option for Linux (especially, in the PMI or LiveCD context) which does not require a partition? If not, this might be a nice enhancement for PMI and LiveCD users, since Knoppix already allows for file-based configuration settings and persistent home.

jd