Browse Prior Art Database

Fixed Disk Sharing via Small Computer System Interface Device Emulation through Compatibility BIOS

IP.com Disclosure Number: IPCOM000110413D
Original Publication Date: 1992-Nov-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 4 page(s) / 139K

Publishing Venue

IBM

Related People

McNeill, AB: AUTHOR [+2]

Abstract

This article describes a method which allows a remote computer with a small computer system interface (SCSI) adapter installed to access a fixed disk in a local computer that also has a SCSI adapter installed, the two SCSI adapters being on the same SCSI bus.

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

Fixed Disk Sharing via Small Computer System Interface Device Emulation through Compatibility BIOS

       This article describes a method which allows a remote
computer with a small computer system interface (SCSI) adapter
installed to access a fixed disk in a local computer that also has a
SCSI adapter installed, the two SCSI adapters being on the same SCSI
bus.

      Target mode allows the adapter to accept commands and transfer
data as if it were a target device (fixed disk, processor device,
scanner, etc.).  With target mode, the SCSI adapter card can be made
to look like any other target SCSI device.  Data can be sent and
received between two adapters which are "processor target devices."
In this way a SCSI local area network can be formed.

      To make for a powerful SCSI local area network, fixed disks
must be shared by the local and remote computers.  Through
transparent target mode, a fixed disk SCSI command can be sent from
the remote computer to the local computer.  Fig. 1 shows the setup
for access to a local fixed disk from a remote computer.  After this
command is decoded, a command can be issued to Compatibility BIOS
(CBIOS) from the local computer to the local fixed disk on behalf of
the remote computer.  For example, a SCSI read command can be sent
from the remote computer to the local computer.  The local computer
decodes this command and gives a CBIOS read command to the local
fixed disk.  It acquires the requested data and sends it to the
remote computer.  This interaction is transparent to the remote
system because the local SCSI adapter is emulating a SCSI fixed disk.
The remote computer is merely giving commands to read some
information through DOS.  DOS is using the standard SCSI CBIOS on the
remote computer.  The fixed disk emulation code on the local computer
needs to share the local computer CBIOS and be transparent to the
local computer user.

      This invention intercepts both the CBIOS software interrupt 13H
an...