Browse Prior Art Database

Diskette Operational Selection Methods for Personal Computers

IP.com Disclosure Number: IPCOM000103703D
Original Publication Date: 1993-Jan-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 6 page(s) / 248K

Publishing Venue

IBM

Related People

Doria, JJ: AUTHOR [+4]

Abstract

Described are two hardware diskette operational selection methods for personal computers (PCs) that enable users to execute applications from various diskette sizes.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 35% of the total text.

Diskette Operational Selection Methods for Personal Computers

       Described are two hardware diskette operational selection
methods for personal computers (PCs) that enable users to execute
applications from various diskette sizes.

      Typically, PCs are equipped with drives that can accommodate
various diskette sizes, such as 5-1/4" and 3-1/2" diameter diskettes.
Generally, software application programs are supplied according to
the user's choice of size to be run in A drive.  In the event the
PC is designed to run the program only in A drive, the diskette size
can present a problem when attempting to run a program not written on
the correct size diskette.

      The first operational method enables the user to choose the
diskette drive subsystem to execute the application program in
accordance with the size of the diskette.  The user chooses the
configuration software and stores the mapping parameter into memory.
The image of this mapping parameter is also copied to the
input/output (I/O) register which is accessible through the use of
mapping circuitry.  Fig. 1 shows the architecture of the mapping
circuitry to enable the chosen configuration to remain, by means of a
battery back-up, after the system power is turned off.  The mapping
parameters are designed to be updated when the power is on and every
time the mapping parameter is changed.  The value of the mapping
parameter designates which drive is to be drive A.  The table below
illustrates the mapping selection for the diskette drives.  Although
four drives are described, any number of drives can be designated.
The default mode designate is as follows:
           MME(0)&MDS(0) Control drive (A:)
           MME(1)&MDS(0) Control drive (B:)
           MME(2)&MDS(2) Control drive (X:)
           MME(3)&MDS(3) Control drive (Y:)
where the X: and the Y: drives are the two next available drives
assigned by an operating system for the diskette subsystem.

      An example of the first operational improvement as associated
with the circuitry of Fig. 1 is as follows:
  If the mapping parameter value is three, then DUAL MUX (I) will
select DS(3) for MDS(0) and ME(3) for MME(0).  Decoder (I) will
activate output Line (3) to be low and the other outputs will be
high.  This condition will force DUAL MUX (IV) to select DS(0) for
MDS(3) and ME(0) for MME(3).  The output Line (1) will force DUAL MUX
(II) to select DS(1) for MDS(1) and ME1 for MME(1).  The output Line
(2) will force the DUAL MUX (III) to select DS(2) for MDS(2) and MEN2
for MME(2).

      The second operational method implements a mapping layer to
selectively load existing operating systems from any diskette drive.
This method enables application programs to be loaded from any
diskette drive directly to I/O ports of the diskette controller.
Both the operating systems and the application programs will adhere
to initial program load (IPL) interface requiremen...