The "UIDE" drivers by Jack Ellis have all been updated to 14-Nov-2013. In this update, UHDD and UDVD2 no longer support "private" caches for user drivers. Reasons for this are a bit involved - read below. As always, you can download binaries and sources from our FreeDOS mirror at iBiblio.
An abbreviated version of Jack's detailed notes are here:
CD/DVD "private caches" were NOT needed to support CD/DVD "kiosk" systems (no hard disk), in Hong Kong or elsewhere. [...] Second, no one yet (to my knowlege) has written any other driver that "calls" UHDD or UIDE to cache its data. [...] Finally, nobody showed ANY "interest" in caching old "video game" CDs for higher game performance. Either such CDs have "disappeared", or game players must now be using RAM-disk drivers, or whatever. [...] So, the 14-Nov-2013 UHDD and UDVD2 drivers are "put back" to having a single cache, that withing UHDD. [...] Any users who ever DO need a "private cache" can get the same results by loading the RDISK driver to set a RAM-disk for their data.