RSX11-M Mailbox Driver --

	Patterned after VSDRV (see Fall '81 DECUS RSXSIG
	symposium tape, [300,120] submission by John Osudar) and the
	VAX/VMS Mailbox driver, this driver performs virtually the
	same functions with a new twist.  The driver maintains a set
	of named queues/mailboxes similar to VS: but rather than
	copying data buffers destined between tasks
	to its internal buffer pool, MB: re-links the I/O packets
	themselves and copies data directly from the writing task's
	virtual address space to the target task's address space.
	This can represent a significant performance improvement for
	large QIOs and is much more immune to running out of
	"pool" because the data is maintained in the requesting task's
	address space.

	There are, however, attendent disadvantages to this scheme.
	By necessity, write-QIOs NEVER complete until a corresponding
	read-QIO (or cancel) operation is issued for the mailbox, and
	tasks with outstanding I/O cannot be checkpointed or shuffled.

	Assemble and build the driver by executing MBDRV.CMD; RSXMC.MAC
	and RSX11M.STB must reside in current system UIC.
	Consult the comments in MBDRV.MAC and documentation in MBDRV.RNO
	for a full description of the driver's design, function codes, etc.
	Several test programs are also included to exercise various
	features of MBDRV; IOPAGE, TIMER and MBTSTn modules are required
	for the test programs.


		Paul R. Sorenson
		AEP/Engineering Computer Support Center
		1 Riverside Plaza
		Columbus, OH 43215