Browse Prior Art Database

Remote Initial Program Load of a Diskless Computing Device via a Standard Serial or Parallel Port

IP.com Disclosure Number: IPCOM000107765D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 3 page(s) / 138K

Publishing Venue

IBM

Related People

Marik, MD: AUTHOR [+2]

Abstract

Some newer personal computers, such as small lap-top or hand-held computers, usually have a display (such as an LCD type) and a touch panel for user I/O, a serial and/or parallel port for communications to other systems and a virtual disk (VDISK) which uses a portion of the Computer's RAM storage as a disk to store files that may be uploaded from an external computer, but such computers lack disk drives (either a hard or a floppy drive) and a conventional keyboard. Such computers are called "diskless". These diskless computing devices require the operating system to be loaded (IPL) using the serial or parallel port and the procedure and programs described in this article.

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This is the abbreviated version, containing approximately 52% of the total text.

Remote Initial Program Load of a Diskless Computing Device via a Standard Serial or Parallel Port

       Some newer personal computers, such as small lap-top or
hand-held computers, usually have a display (such as an LCD type) and
a touch panel for user I/O, a serial and/or parallel port for
communications to other systems and a virtual disk (VDISK) which uses
a portion of the Computer's RAM storage as a disk to store files that
may be uploaded from an external computer, but such computers lack
disk drives (either a hard or a floppy drive) and a conventional
keyboard. Such computers are called "diskless".  These diskless
computing devices require the operating system to be loaded (IPL)
using the serial or parallel port and the procedure and programs
described in this article.

      A PC-host, such as an IBM PS/2* or the like, connects to the
diskless  Computing device via either a serial or parallel
communications port.  The PC-host provides the means and the source
data by which the diskless Computing device is initialized with DOS
and any applications loaded onto its VDISK.

      Current IBM personal computers start initial program load (IPL)
by an interrupt 19hex (in BIOS) which sets up the system to access
the Bootstrap record  found on  the operating  system diskette: track
0, sector 1 (DOS).  The PC BIOS provides the interrupt 13hex, the I/O
to the floppy disk or hard drive, to retrieve the data from the
magnetic media as per the Bootstrap record and load it into RAM.

      IPL of a diskless PC begins with the interrupt 19hex Bootstrap:
however, when it invokes interrupt 13hex to do the actual disk I/O
function a remote disk server takes over to send  the interrupt 13hex
request to the remote PC-host for processing.   The PC-host runs the
application that performs the actual interrupt 13hex requests for the
diskless PC.  The results from  the interrupt  13hex operation  on
the host are transmitted back to the diskless PC.

      For serial port operations, the BIOS in the diskless PC
provides the interrupt 13hex vector to point to a routine called
"Remote Disk Server".  It also provides interrupt 0Chex vector that
points to a routine called the "Comm Server" which services UART
transmit and receive interrupts from IRQ4 (serial 1).   (Note: IRQ 3
(serial 2) interrupt vector 0Bhex can also be used.)  These routines
use data buffers which are located in the highest available RAM.  The
memory size field in the BIOS data area is reduced so that these
memory buffers can be for the exclusive use of the remote disk server
and Comm Server routines.  The host PC's application also uses
interrupt 0Chex to send and receive data buffers.  This is shown in
Fig. 1.

      As the "diskless" PC's BIOS makes its first attempt to access
the diskette using interrupt 13hex to start loading the bootstrap
record, the Remote  Disk Server routine will intervene and create an
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