CMS Jumbo tape drive and 2.3.2

[uhclem at trsvax.UUCP]

<>
R1>The last time I ran up against one of these drives, I had the same
R1>problem. A client asked me to move it from a DOS box to their new SCO
R1>XENIX unit. After having the same kind of problems,I finally found out that
R1>there are two versions of the PAL on the controller board...one for DOS, and
R1>one for XENIX (or so the fourth person I talked to at CMS said!).

Quite right.  We convinced CMS to make the PAL change for XENIX a couple of
years ago because the original (DOS) PAL requires a command protocol that
takes 10 - 15 Msec per command WITH ALL x86 INTERRUPTS DISABLED!  This did
dreadful things to the RS-232 performance on your XENIX system, but it
didn't make any difference under single-tasking DOS.  A "new" PAL reduces the
handshaking timing down below 1 msec, so hopefully you don't drop too many
RS-232 characters.  But it does mean the drive PAL has to match the drivers.

The Techmar/CMS QIC-60 system also needed a PAL change because interrupts
didn't work and no one had noticed or cared until we tried to use it with
XENIX.  "It works OK under DOS, what more do you want?" was heard a lot. :-(

					"Thank you, Uh Clem."
					Frank Durda IV @ <trsvax!uhclem>
				...decvax!microsoft!trsvax!uhclem
				...hal6000!trsvax!uhclem