Browse Prior Art Database

Memory Remap Determination Method for Personal Computers

IP.com Disclosure Number: IPCOM000114027D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 93K

Publishing Venue

IBM

Related People

Merkin, CM: AUTHOR

Abstract

Described is an architectural implementation which provides a method for determining the minimum amount of memory required when running an Adapter Descriptor Program (ADP), as used in Personal Computers (PCs). The implementation utilizes an algorithm in the determination of the optimal amount of system memory that resides within a specific address range.

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This is the abbreviated version, containing approximately 53% of the total text.

Memory Remap Determination Method for Personal Computers

      Described is an architectural implementation which provides a
method for determining the minimum amount of memory required when
running an Adapter Descriptor Program (ADP), as used in Personal
Computers (PCs).  The implementation utilizes an algorithm in the
determination of the optimal amount of system memory that resides
within a specific address range.

      In prior art, a PC setup program would call an ADP repetitively
in order to obtain an area of memory within an address space below
16MB.  This was particularly true for other adaptors which required
non-system memory space within that area.  Typically, when the setup
program called the ADP, the ADP was requested to remap the minimum
amount of system memory configured to respond to addresses below the
16MB address line.  That memory would be configured to respond to
addresses above the 16MB address line.  This is because the ADP was
not instructed as to how much non-system memory address space was
required.  Since many PC operating systems make use of only the
system memory that resides in the address range below 16MB, it became
imperative that the ADP optimize the amount of system memory that is
configured within this address range.

      The concept described herein is designed to optimize the amount
of system memory residing within an address range below 16MB.  An
algorithm is used to enable the ADP to deduce the size of the
non-system address space required by the setup program.  It is based
on the system memory configuration that the ADP determined on the
setup program's previous call to the ADP.  The algorithm uses the
amount of memory that was previously configured to respond to
addresses below 16MB and uses the currently installed memory bank
sizes to perform this deduction.  The output of the algorithm is a
memory configuration that results in the optimal amount of system
memory residing within the address range below 16MB.

      Each time the ADP returns to the setup program, the ADP stores,
in static variables, the number of megabytes of memory that has been
configured to respond to addresses both below and above the 16MB
address line.  Whenever the ADP is called by the setup program to
provide the remap function, the ADP performs the following functions:
 1.  Determines the amount of memory previously configured for the
     non-system memory present in the system.  This value is
     determined by subtracting the amount of memory previously
     configured to "live" below 16MB from 16.  Since the s...