Ref: 11640105
Title: Use Low Density Media With NCS/150 and Series/1 Devices
Date: 1/4/91

Copyright 3Com Corporation, 1991.  All rights reserved.

3Com Series/1 platform devices and the NCS/150 use a LOW DENSITY disk drive.
The required media (diskette) is 1 MB unformatted, 720 KB formatted.

For years, TEAC FD-55FR-511-U low density disk drives (known as "FR" disk
drives) have been implemented in 3Com Series/1 platform devices and NCS-150s.
In mid-1990, TEAC had difficulty supplying the FR disk drive, so two other
low density drives were substituted.  These were TEAC models FD-55FV-52-U
and FD-55FV-13-U, (known as "FV" disk drives).  Approximately 250 FVs were
substituted.  (Note:  3Com currently uses only FRs.)

Although the FR is a low density disk drive, it will successfully format
and write information to high density media.  The FV will NOT copy software
to high density media.  If you have been using high density media on
the FR drive and you attempt to use it on an FV drive, you may think that
the FV drive is not working properly, because it will not copy the software.
However, the problem is with the media, not the disk drive.

3Com ships its software on low density media, and 3Com manuals state that
customers should use low density media when making working copies of 3Com
software.  It is assumed that the user knows the difference between high and
low density media.  However, it can be difficult to tell the difference
between media types because suppliers may ship it unmarked or with obscure
labeling.

   Low Density  = 1 MB unformatted, 720 KB formatted.  Also called
  "Double Sided, Double Density"
   High Density = 1.6MB unformatted, 1.2MB formatted.  Also called
  "HD," or "MD2-D" with 96 tracks per inch (TPI)

