Browse Prior Art Database

Dual Interface Diskette Drive for Personal Computer Systems

IP.com Disclosure Number: IPCOM000103905D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 72K

Publishing Venue

IBM

Related People

Strunk, JR: AUTHOR [+2]

Abstract

Described is a hardware implementation which allows the use of small computer system interface (SCSI) diskette drives to work in existing personal computer (PC) systems. The design is such that minimal software changes and no system hardware changes would be necessary to allow full backward compatibility with existing application programs. This applies to systems which already have a diskette controller and a SCSI controller.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Dual Interface Diskette Drive for Personal Computer Systems

      Described is a hardware implementation which allows the use of
small computer system interface (SCSI) diskette drives to work in
existing personal computer (PC) systems.  The design is such that
minimal software changes and no system hardware changes would be
necessary to allow full backward compatibility with existing
application programs.  This applies to systems which already have a
diskette controller and a SCSI controller.

      Diskette drive controllers and phase lock loops (PLLs) were
originally designed to be separate from the diskette drive unit.
Application programs were designed to have the diskette controllers
operate through the diskette drive basic input output system (BIOS).
There are certain programs, which go around the diskette drive BIOS,
and interface directly with the diskette drive controller.

      The current diskette drive industry is moving towards SCSI as
the interface for all high capacity 3.5" diskette drives.  This would
apply to drives which are at least 10 MB in formatted capacity.  Many
of these high capacity diskette drives are read and write compatible
with existing 720 KB, 1.44 MB and 2.88 MB formatted diskettes.  Many
application programs written on 720 KB, 1.44 MB and 2.88 MB diskettes
will work on these new high capacity SCSI drives.

      However, certain programs which go around diskette drive BIOS
can encounter problems when reading or writing with the SCSI
interface.  Typically, these types of problems go directly to the
diskette controller to implement copy protection schemes or for
alternative drive control reasons, such as searching for the drive
index pulses.  As a result, SCSI drives are not compatible with this
type of existing software.  Generally, it is difficult to write a
software driver which properly emulates the diskette controller
timings for these programs.  Also, since software access to the
diskette controller registers is not possible with a SCSI only
diskette drive, changes would be required to the s...