Subject: More DECmate RX50 Images on sunsite archive

From: Charles Lasner <[email-masked]>
Date: Tue, 19 Jul 1994 10:48:19 -0400 (EDT)

The PDP-8/DECmate archive on sunsite.unc.edu continues to grow by leaps 
and bounds!

One of the fast-growing areas is the RX50 diskimage area in 
//pdp-8/diskimages/rx50/teledisk and the associated labels directory.

Each file is a complete image of a standard RX50 diskette and an
associated label suitable for printing out on sticky address labels of a
common size in the US (3.5" x 15/16").  Each label file is 6 lines high
with only the interior 4 or less lines actually used.  Once the first
label is lined up (there is a test label file for alignment purposes,
etc.) the entire lot of .LBL files can be printed in succession with
ordinary print routines capable of normal printing with CR/LF only, etc. 

The .LBL file is available in the labels directory and is also included 
in the teledisk directory as well (indirectly).  Each file in the 
teledisk directory is actually a .ZIP file containing both the .LBL file 
and also a .TD0 file which is the TELEDISK image of the RX50 diskette.  
PKZ204G.EXE or equivalent unzip are required to produce the files from 
within the .ZIP files.

The .TD0 files are standard teledisk 2.x files which can be converted 
directly to the RX50 diskettes using the shareware version of teledisk V 
2.12 or greater.  (Note: versions greater than 2.12 are *not* 
shareware!)  Required hardware is a PC with a good quality (such as TEAC 
FD55GFR) 5.25" HD drive.  In spite of known bugs in Version 2.12, the 
provided files will convert correctly into viable RX50 diskettes.

As with all teledisk usage, it's mandatory to provide the correct media
for the job: HD diskettes will *not* work on RX50 drives due to the
radically different coercivity, etc. parameters of HD formulation.  The
original diskettes mandated are MD1DD or equivalent, which is actually
360K-type diskettes honed to allow 96 TPI rather than 48 TPI, but still
intended for large-signal operation at 250 KHZ, not 500 KHz as is used in
HD diskettes, etc.  However, modern diskette production typically 
actually produces well-honed media, albeit untested beyond 48 TPI 
requirements.

Thus, the best alternative is to use cheap DSDD diskettes, even one-sided
ones, preferably without hub rings if possible.  (Note: removing hub rings
incompletely is worse than not removing them at all!  Hub rings in turn
cause eventual registration errors because all 96 TPI diskettes are far
more critical due so smaller recorded area than 48 TPI diskettes, thus far
more critical hub alignment is required.  As hub rings age, they cause the
diskette to "drift" more readily.  Thus, all HD diskettes which are
*always* recorded at 96 TPI are produced without hub rings.  However, this
is not done because of their higher frequency, rather the higher TPI which
is shared by the RX50 requirements as well, etc.)  If a batch of disks 
produces unreliable results, try another batch.  They're cheap enough to 
waste a few boxes on until you get a good batch.  (And if the hub rings 
cannot be removed, just recycle the disks as 360K disks every few months 
of heavy usage or equivalent.  On hard-disk based DECmates, this could 
literally add up to years as the diskettes are only seldom used to 
install software and little else, etc.  In such cases, the only heavy 
usage of diskettes generally is for backups and/or inter-machine file 
transfer via diskettes, etc.  In these few cases, or for diskette-only 
machines used heavily, etc., MD1DD or equivalent should be used for long 
life.  Expect to pay a high price for a box or two, but more shouldn't be 
needed as the data can be copied from a seldom-used diskette to a 
heavily-used MD1DD diskette, etc.)

Archive files are available for a few common DECmate utilities such as
Typeasy, GTE, as well as a complete set of WPS 2.3.0 diskettes including a
US DECspell.  (UK (ize, ise) versions will eventually be available.  Does
anyone have any information on the allegedly sold legal dictionary
variant?)

Additional files include CP/M-80 and a few major CP/M-80 packages sold by 
Digital specifically for the DECmate such as MultiPlan.  (Note: this 
archive is not going to be a general repository for generic CP/M-80 
packages; only programs of specific use on the DECmate will be provided.  
Additionally, there could be legal complications distributing files that 
could be run on other architectures!)  DEC's MS-DOS 2.11 for the DECmate 
II with XPU is also available.  (Again, only programs of specific use on 
the DECmate will be provided to avoid the same legal complications, etc.)

Recent arrivals to the archive include the DM-112 release diskettes of
COS-310 for DECmate.  The first diskette is a complete diskette-based COS
system capable of transferring itself to a hard disk volume on a DECmate
II or III+. 

The second diskette (DM1122) is essentially a utility to make up for
inadequacies of the standard Master Menu, which apparently does not quite
correctly allocate a COS volume, although I understand that there are
COS-specific commands to at least conditionally correct the problem.  (I
suspect that the problem is that COS commands assume the COS volumes are
of a standard size, thus if the volumes are allocated to a non-standard
size, the COS commands may not fully work.  In any case, Master Menu
produces volumes that are not immediately useful to COS in spite of screen
output to the contrary.  COS commands may be able to correct this
situation.  Using the provided utility instead of Master Menu will produce
correct COS volumes immediately.  Note that there is an OS/278 parallel 
to this, but there is an OS/278 program FIXDIR to correct the problem 
explicitly.)

I would appreciate it if someone could write up a small FAQ file for COS 
usage taken from its manual, which is apparently not available in 
machine-readable form.  This could including some working basics, as well 
as explaining all of the issues related to installing COS, including 
anomalies of the volume problems, sizes, mounting considerations, 
work-arounds etc.

The next set of diskettes will be related to OS/278 V2.  In a separate 
post, I'll explain some specifics.

cjl