Presumably, you're referring to the need to have a supported 20/40MB hard-drive installed in the RLX-B in order use an XT-IDE card instead, as the XTIDE Universal BIOS fails to initialize otherwise?

If so, I still feel like this should be solvable within the XUB code itself, as I've not encountered similar issues with other bootable SCSI or IDE cards in the RLX-B. That said, the RLX-A doesn't exhibit the same issue with XUB initialization, so there's certainly some difference between the A and B BIOS versions at play. Indeed, swapping an RLX-A BIOS chip into an RLX-B allows an XT-IDE card to properly boot, but sans video, as the video BIOS isn't compatible between the two system revisions. Some sort of kludge ROM that replaces the system portion of the RLX-B BIOS with that from the RLX-A could conceivably act as a workaround.

With my own RLX-B, I've opted to replace the internal drive with an "XTA2SD" board, but for no other purpose than allowing me to boot from an installed XT-IDE card instead, all while keeping the system completely silent. With the larger storage capacity provided by the XT-IDE card, and sound options provided by the Tandy PSSJ, RS-232 MIDI, and an OPL3LPT, the RLX isn't wanting for much. :)  -- Cloudschatze