The Free On-line Dictionary of Computing (18 March 2015):
(SMP) Two or more similar processors connected
via a high-bandwidth link and managed by one operating
system, where each processor has equal access to I/O devices.
This is in contrast to the "compute server" kind of
parallel processor where a front-end processor handles all
I/O to disks, terminals and local area network etc.
The processors are treated more or less equally, with
application programs able to run on any or perhaps all
processors in the system, interchangeably, at the operating
system's discretion. Simple MP usually involves assigning
each processor to a fixed task (such as managing the file
system), reserving the single main CPU for general tasks.
OS/2 currently supports so-called HMP (Hybrid
Multiprocessing), which provides some elements of symmetric
multiprocessing, using add-on IBM software called MP/2. OS/2
SMP was planned for release in late 1993.