🚀 go-pugleaf

 >We're looking at a real-time application involving several oddball
 >gizmos communicating with the serial ports at 9600.  These have
 >to be multitasked with some decidedly non-trivial programming
 >involved, and have to be responded to in some cases inside 25ms or
 >  all kinds of disasters will occur.

 Real Time means having a guaranteed response time (not necessarily
 an instant one though).  Many general purpose real time OSes may
 allow a guaranteed response of around 30ms to a single task.  In
 cases where there are several devices it gets compliacated - what
 happens if they all request attention at the same instant - the
 first (most imortant ?) may get 25ms or 30ms response, the rest
 will be after that depending on the work done for the preceeding
 tasks.

 I suggest that you look at a dedicated multi-tasking RTOS, at least
 to find out what is required, such as FlexOS.