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Method Allowing Small Computer System Interface Adapters to Coexist with Other Hardfile Adapters

IP.com Disclosure Number: IPCOM000113759D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Beam, S: AUTHOR [+4]

Abstract

Disclosed is the use by Power-On Self-Test (POST) of the first entry in a Small Computer System Interface (SCSI) record table to boot the System Partition, allowing other hardfile adapters to coexist with SCSI adapters in an IBM Personal System/2* Model 90 or 95. This method is implemented by modifications to POST and BIOS code and to the IBM Utility. Without the implementation of this method, when a hardfile adapter other than an IBM SCSI adapter is installed in a Model 90 or 95, POST attempts to boot the System Partition from the wrong hardfile.

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

Method Allowing Small Computer System Interface Adapters to Coexist
with Other Hardfile Adapters

      Disclosed is the use by Power-On Self-Test (POST) of the first
entry in a Small Computer System Interface (SCSI) record table to
boot the System Partition, allowing other hardfile adapters to
coexist with SCSI adapters in an IBM Personal System/2* Model 90 or
95.  This method is implemented by modifications to POST and BIOS
code and to the IBM Utility.  Without the implementation of this
method, when a hardfile adapter other than an IBM SCSI adapter is
installed in a Model 90 or 95, POST attempts to boot the System
Partition from the wrong hardfile.

      At the end of POST, when it is time to transfer control to an
operating system, POST searches for a valid boot record, using a
default sequence consisting of a diskette drive, a hardfile, and an
Remote Program Load (RPL), which connects the system to another
system through an adapter.  The user has a choice to override this
default sequence by defining a Selectable Boot Sequence using the IBM
Utility residing in a special area of the hardfile protected from the
operating system by POST programming the SCSI hardfile adapter.  This
special area, called the System Partition, is complete with its own
boot record, acting as a Reference Diskette stored on the hardfile,
containing Setup and IBM Utilities.

      When POST determines that the time to boot the System Partition
has arrived, either because a user request to do so has occurred, or
because of an error in the system, a series of programming events
occur.  First, POST determines which hardfile has the System
Partition.  This SCSI hardfile is assigned the number 80h and the
letter C: by making it the first entry in the SCSI Record Table,
which is part of the Extended BIOS Data Area.  This drive is then
known as the "first SCSI."  Next, the SCSI controller is programmed
not to protect the System Partition from reads and writes.  Finally,
BIOS is programmed to modify each read and write to the hardfile 80h
so that the System Partition is accessed instead of the operating
system boot record.  Thus, when POST loads the boot record from C:,
it is really loading a System...