Browse Prior Art Database

Wideline Display Or Standard VGA Using 5-Wide Characters

IP.com Disclosure Number: IPCOM000121105D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 4 page(s) / 175K

Publishing Venue

IBM

Related People

Bowater, RJ: AUTHOR [+2]

Abstract

The standard VGA (Video Graphics Adapter) on IBM PS/2* planars does not support 132-character-wide displays for 3270 Model 5 emulation when used in its standard modes with IBM monitors. Described is a technique by which a 132-character-wide display can be produced on adapter and monitor hardware which normally supports only 640 pixels along each scanline. It is achieved by using a slightly wider display of 660 pixels, with each character being only 5 pixels wide. To improve the quality of these narrow characters, a form of anti-aliasing is used in which each pixel of a character can be off, full intensity or at an intermediate value. The intermediate intensity pixels are used to 'round-off' characters, significantly improving legibility.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 43% of the total text.

Wideline Display Or Standard VGA Using 5-Wide Characters

      The standard VGA (Video Graphics Adapter) on IBM PS/2*
planars does not support 132-character-wide displays for 3270 Model 5
emulation when used in its standard modes with IBM monitors.
Described is a technique by which a 132-character-wide display can be
produced on adapter and monitor hardware which normally supports only
640 pixels along each scanline.  It is achieved by using a slightly
wider display of 660 pixels, with each character being only 5 pixels
wide.  To improve the quality of these narrow characters, a form of
anti-aliasing is used in which each pixel of a character can be off,
full intensity or at an intermediate value.  The intermediate
intensity pixels are used to 'round-off' characters, significantly
improving legibility.

      The family of IBM 3270 workstations are capable of displaying
character data in four display formats, known as 3270 Models 2,3,4
and 5.  Models 2,3 and 4 display 80 characters across the width of
the screen, and Model 5 displays 132 characters.  The number of rows
and columns for each Model is shown in Figure 1.  In addition to the
number of lines shown, a narrow divider line (3 or 4 scan lines) and
a full width additional character row known as the Operator
Information Area (OIA) are displayed at the bottom of the screen.
The VGA chip, which is packaged as an integral part of all IBM PS/2
systems, has a horizontal resolution of 640 or 720 pixels across the
width of the screen, determined by the fixed pixel clock frequency
oscillators located on the system planar (25 MHz and 28 MHz).  The
number of vertical lines displayed by the VGA is programmable but,
when IBM monitors such as the 8513 are used with the VGA, the number
of vertical lines is limited to 350, 400 or 480.  The horizontal
resolution of 640 and 720 is used to provide 80 characters of 8 or 9
pixels aside. Neither resolution is adequate for the 3270 Model 5
requirement of 132 characters.  The corresponding resolution for 8-
and 9-wide characters would be 1056 and 1188 pixels, respectively,
which is beyond the capability of the VGA or the VGA monitors.

      The disclosed technique uses a resolution of 660 pixels x 395
lines for 3270 Model 5 emulation on the standard VGA which is done by
slightly widening the standard 640 pixel wide display, and leaving 5
blank lines on a 400 line display.  This is shown diagrammatically in
Figure 2.  Each character box position is 5 pels wide by 14 pixels
deep with a divider line of 3 scan lines with the middle line drawn
on.  Characters occupy the full 5 pixel width by 12 lines deep in
each character box, with the bottom  2 lines being used for the 3270
cursor.  An example of the 5-wide character format is shown in Figure
3.  The 660 x 395 line mode is not one of the standard modes
supported by the VGA BIOS (Basic Input Output Services) of PS/2 and
special programming of the VGA registers is required.  The displa...