I decided to give this a try to see how well it works. After a little trial and error I can say this is a really cool option if you have writable memory between 640K-1MB. I tried it out in my NuXT v2.0 motherboard which has UMBs enabled for C800-DFFF. I specified C800 as the start address in the XTIDE BIOS UMB option. I then had to move the starting address for USE!UMBS.sys to C840 so the XTIDE drive variables would not get overwritten. All is working fine now and I have a full 640K instead stealing 1K from MS-DOS. Next up I plan on trying this with my Tandy 1000 SX and Tandy 1000 SL/2 as you can't enable XTIDE Full Operating Mode as this conflicts with the Tandy 1000 stealing the top 16K for video memory. This should now fix that issue as I have a Lo-Tech 1MB memory card in both systems.