Can you do this in any UNIX?

[gregory.p.kochanski]

As a experimental physicist, I find myself often wanting to do strange
things to computers.  I have a particular set of hardware that I'd dearly
like to run with a unix box, rather than MS-DOS, but it requires some
serious speed.  Basically, I need to be able to read a single word
from some hardware in 50 microseconds or less (and write in the same
smount of time).  Can any unix do this, perhaps by locking processes into
the CPU and allowing some end-run around device driver overheads?
That and C++, too?