Chapter 7: The Screen Display - NCR PC4I Technical Reference

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Chapter 7
The Screen
Display
The NCR PERSONAL COMPUTER can drive both a monochrome
and a color display by means of adapter cards. Two
types of adapter card are available: the character
display card enables the monochrome display of all
256 characters in the character generator and
includes 4 KB of memory; the graphic display card
additionally supports "all points addressable"
graphics and contains a 32 KB memory.
The 32 KB memory of the graphic display card can be
upgraded to 64 KB, thus enabling you to make full use
of the high resolution (640 x 400 pixels) capability
of the NCR PERSONAL COMPUTER color CRT.
Both the monochrome and color CRT are driven by a
6845 controller. A dual port configuration is used so
that CPU access and CRT controller can access video
RAM independently of one another.
AVAD.ABLE ADAPTERS
Only one version of the NCR PERSONAL COMPUTER
contains the character display card as standard: the
monochrome, single diskette drive, 256 KB memory
system. All other versions contain a graphic display
card. The video memory address areas of the two cards
do not clash (all video RAM lies within the CPU
address area). It is possible to connect a monochrome
monitor to a graphic display card and it is possible
to add an external monitor to the NCR PERSONAL
COMPUTER by means of an additional adapter card. A
number of industry standard monitors can be
connected: if the internal monitor is driven by a
graphic display card, the external monitor must be
connected by means of a character display card, and
vice versa. Different cards are used for a type of
display (character/graphic), according to whether the
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