Browse Prior Art Database

Emulation of Personal Computer Displays On AIX Virtual Terminals

IP.com Disclosure Number: IPCOM000101323D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 84K

Publishing Venue

IBM

Related People

Blackard, JW: AUTHOR [+3]

Abstract

Disclosed is a method by which Personal Computer (PC) displays may be emulated on AIX* virtual terminals. The Personal Computer AT* Simulator on AIX uses this method for emulating PC displays. The method described uses multiple processes communicating where one process is simulating PC instructions, and up to two other processes are managing the AIX virtual terminals emulating the PC displays.

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

Emulation of Personal Computer Displays On AIX Virtual Terminals

       Disclosed is a method by which Personal Computer (PC)
displays may be emulated on AIX* virtual terminals.  The Personal
Computer AT* Simulator on AIX uses this method for emulating PC
displays.  The method described uses multiple processes communicating
where one process is simulating PC instructions, and up to two other
processes are managing the AIX virtual terminals emulating the PC
displays.

      When the Personal Computer AT simulator is started, it forks up
to three separate processes.  One process is forked for the
instruction simulation.  A process is also forked for each display
requested (up to two).  Each display process accepts input from the
keyboard, and updates the screen image on the AIX virtual terminal
emulating the PC display.  The instruction simulation process
translates PC instructions to equivalent sequences of instructions
for the machine-running AIX.  The instruction simulation process also
notifies the display process(es) of any changes to the screen image.
These processes use an AIX-shared memory segment to share data.

      When forked, a display process opens a virtual terminal on the
user-requested display.  The AIX Graphics Support Library (GSL) of
subroutines is used for output to the virtual terminal.  Keystrokes
are retrieved using the AIX read() system call.  The keys are
translated from AIX keyboard scan codes to PC keyboard scan codes,
and put into a buffer in the shared memory segment.  An interrupt is
simulated to the instruction simulator process, which then processes
the PC keystrokes.

      The instruction simulation process monitors input and output to
the PC display video buffer which contains the data which is
presented on the PC display.  when a change is made to the video
buffer, a display list is updated.  Thi...