AFAIK, it should be as you say an enchanced version of CGA. I
believe that had the ability to show 640x200 with 16 colours where
normal CGA only showed 4 colours in that resolution. It was the card
used in the famous Amstrad PC1512 !!!
The Plantronics PC+ Colorplus Graphics Adaptor was produced by the
Plantronics subsidiary of Frederick Electronics in 1982 as an
alternative to the IBM CGI (*NOT* EGA) Adaptor. It is essentially two
CGIs (even has two separate boards pegged together). It sold for $475
including some basic software.
What this permitted was four bit planes in 320x200 (i.e. 16 colors)
and two bit planes in 640x200 (i.e. four colors) where the IBM CGA
only produced four (low res) and b&w 'high' res. There is also an
undocumented 160x100 mode and judicious use of the control registers
could produce literally stunning results.
The card came with full support for BASIC for defining the additional
bit planes and the IBM PC System Board switches were to be set to
80x25 Color monitor (2-ON 5-ON 6 OFF). You can set whether you
want single pixel or double pixel characters as the default (The
original IBM PC actually doubled the number of horizontal pixels
for the lines forming characters because when used with the TV
the single line characters would 'bleed'. This is not a problem with
an RGB monitor and can be turned off. (move the jumper from WJ4
to the two pins comprising WJ5 on the top of the card to get single
The card came with an optional program "The Draftsman for Colorplus"
which let you design and import .bmp files from various applications
like Visicalc and convert them to 16 colors from the four they
produced. Additionally you could use this product to produce Slide
Shows and print to a color plotter.
There were fourteen applications originally which supported the
Plantronics including Videotex Communications Videotex (which I
understand was in widespread use in Canada at the time via NAPLPS
Information Servers could produce near real-time images from a
The output to a quality CGI Monitor like the NEC was quite impressive
and very fast for 8088 standards. It still amazes me how, with
dithering techniques, you can get excellent graphics even at
I don't know whether Plantronics later produced an EGA Compatible
Card. One of the features of the IBM PC was that it could support
dual monitors - i.e. you could connect a monochrome and a CGA at the
same time. Many programs such as Visicalc, Lotus, and Supercalc would
let you view and work with a spreadsheet on the monochrome monitor
while simultaneously displaying charts and graphs on the Color
Monitor. The Plantonics is well-suited for this type application.
I have full documentation, software, and demos on 5 1/2" diskettes.
Unfortunately I do not have a scanner and it is a fair number of
pages. If you would like copies of any of this stuff, I would have to
charge you for my costs in getting it XEROXed and Mailed, etc.
I hope you will have some fun with it as it forms the basis for a very
good introduction to the IBM Graphics Interface including video memory
interleaving, bit planes, CRT Controller Register Use, and so on.
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