Browse Prior Art Database

802.2 VDD Memory Allocation in a VM Boot Environment

IP.com Disclosure Number: IPCOM000112519D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Bartek, B: AUTHOR [+3]

Abstract

A method is described to enable DOS Virtual Device Drivers, VDDs, running in OS/2* 2.0 VM Boot mode to allocate and access physically contiguous 'normal' memory. This method is necessary because in OS/2 2.0 VM Boot mode, DOS VDDs cannot allocate physically contiguous memory via the Virtual Device Help API.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 67% of the total text.

802.2 VDD Memory Allocation in a VM Boot Environment

      A method is described to enable DOS Virtual Device Drivers,
VDDs, running in OS/2* 2.0 VM Boot mode to allocate and access
physically contiguous 'normal' memory.  This method is necessary
because in OS/2 2.0 VM Boot mode, DOS VDDs cannot allocate physically
contiguous memory via the Virtual Device Help API.

      In OS/2 2.0, there is a concept of Virtual DOS Machines, VDMs,
which allow DOS applications to run within OS/2 2.0.  A special case
for VDMs is referred to as VM Boot mode.  In this mode an actual copy
of a specific version of DOS is run within the session allowing the
DOS applications access to the exact implementation of that DOS and
not just the emulated version provided by the OS/2 2.0 operating
system known as Virtual 8086 mode.  When a DOS application runs in
Virtual 8086 mode, a VDD may allocate normal DOS memory.  However,
when a DOS application runs in a VM Boot mode session, the allocation
of normal DOS memory is not allowed by the OS/2 2.0 operating system.
Therefore, an alternate mechanism to get the necessary memory
allocated for the VDD is needed so that the DOS application interrupt
request can be satisfied.

One preferred method is to include a simple DOS device driver, whose
purpose is to allocate normal DOS memory for use by the VDD.  When
the DOS device driver initializes it is given the knowledge of how
much memory the VDD needs by the VDD.  This value is the maximum
amoun...