TPC -- Fast Tape Copy

26-Jun-91

   This is version 1.75 of TPC, the fast tape copy program.    There
are several enhancements over previous versions.   These include:

1.	Some unknown enhancer added magtape devices MU: and MA: to
	the device list.

2.	Someone also added the /MI (Magtape In) and /MO (Magtape Out)
	switches to force a device to be treated as a tape (useful
	if new tape devices are ever defined).

3.	I fixed a serious bug in the AST routines: none of them ever
	saved R0-R5!!!   Since only one AST routine could ever execute at
	a time (and the mainline code was suspended), this bug has gone
	undetected for 14 years.   It finally bit me when I tried to go
	disk-to-tape from a high-speed caching disk controller.   The
	first QIO completed (and triggered the AST) before the second QIO
	was issued.   The registers were then clobbered, causing the
	remainder of the setup code to execute incorrectly. 

   There is still at least one more problem to be fixed when someone
finds some time.   On RSX-11M-Plus, if the tape is not mounted foreign,
the program will simply hang.   This condition needs to be checked for
and reported.

	Alan E. Frisbie
	Flying Disk Systems
	4759 Round Top Drive
	Los Angeles, CA 90065

	(213) 256-2575