Browse Prior Art Database

Readable Address Location in Real Time Clock to Lock Security System Flags for Personal Computers

IP.com Disclosure Number: IPCOM000104685D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Clarke Jr, GL: AUTHOR [+2]

Abstract

Described is a software implementation for personal computer (PC) systems to provide a lockable addre ss in the real time clock memory to permit storage of system flags that may not be altered after locking, but may be read.

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

Readable Address Location in Real Time Clock to Lock Security System Flags for Personal Computers

      Described is a software implementation for personal computer
(PC) systems to provide a lockable addre ss in the real time clock
memory to permit storage of system flags that may not be altered
after locking, but may be read.

      With the introduction of C2 security systems, it was necessary
to interrogate system flags whereby power-on system test (POST) g
enerated the flags and stored them in address 19 of the PC's real
time clock.  Once the flag was locked by way of port 92, it may only
be read.  The concept described herein distinguishes itself from the
password lock in the following way:  The password is typed by way of
the keyboard, then locked by way of port 92 and becomes read and
write protected, but is not part of C2 security.  In this way POST
stores the system flags that may not be altered after locking.

      The concept utilizes random access memor y (RAM) address
location 019 which becomes a read only byte once POST sets its lock
by writing bit 5 in port 92 to one.  The figure shows the register
settings for port 92.  This permits POST to store system flags that
are available to be read at a later time.  The flag lock, once set by
POST, can only be cleared by a power-on reset.  All write access
attempts to address 19 are ignored, thereby guaranteeing the
integrity of the flag lock function.

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