The XROS thing sounds sort of like the PenPoint OS -- which was used with the EO 440 and EO 880 tablet + Cellphone-connected computers that came out around the same time as Newton (early 90s) - but with larger screens and cellular voice/data/fax connectivity (optional). Their tagline was "The Pen is the Point". Besides having a WACOM tablet as the pen-input device (requiring a driver), and baking in the notion that (at that time was true): connectivity was sporadic, and therefore you had to be opportunistic when you got a reliable cell signal (or were plugged into a phone jack). Those two ideas sure as
heck did not require a whole new OS to support. But PenPoint built a company to market said OS.
https://en.wikipedia.org/wiki/PenPoint_OS?useskin=vector Interestingly, this company ended up being folded into EO itself, as there seemed to be no market for a pen-based OS.
The EOs https://en.wikipedia.org/wiki/EO_Personal_Communicator?usesk... used the AT&T Hobbit chipset, which was a descendant from the CRISP architecture. https://dl.acm.org/doi/pdf/10.1145/30350.30385 by Dave Ditzel et al. The architecture was informed by examining millions of lines of unix C code; the arch was an attempt to execute C code well. https://en.wikipedia.org/wiki/AT%26T_Hobbit?useskin=vector It was a beautiful overall design. The design focused on fast instruction decoding, indexed array access, and procedure calls. The 32-bit architecture of Hobbit was well-suited to portable computing, and almost ended up in the Apple Newton. The manual is possibly worth a peruse: http://www.bitsavers.org/components/att/hobbit/ATT92010_Hobb...