robeth, when you are loading an ISO from the ms using the np9660 driver, you are effectively arleady running a cached UMD. That is what the driver was designed to do, M33 just changed it so it didn't do the caching bit and just read the ISO direct. If you cached a ISO to the memory stick , you would just have 2 copies of the same data on the disc and actually slow data read rates overall because there would be more going on in the MS.