The colour graphics is in the form of a kit. It consists of two boards,
one is a colour modulator (originally designed for TV games), and the
other a micrographics board. All components including the 12 chips,
connecting wires, etc. are included, as are the instructions,
programming notes and demo programs.
The kit provides six colours (red, green, yellow, blue, magenta, cyan)
plus of course black and white. Each character on the screen is
sub-divided into four “pixels”. Any combination of pixels may be
displayed as any colour, therefore the screen has a resolution of 3072
“cells”. Also the background may be selected as any of the colours by
interfacing with the PIO.
Construction is very easy, the instructions being quite good. I had no
problems although there are 17 connections to the Nascom board and 3 to
the P10 socket. This tends to make it took like a “bird’s nest”, but
with a bit of thought it can be neatened considerably. When connected
“bread board fashion” the kit worked extremely well, but I did not have
enough room in the case to mount the two boards as directed – so, I
mounted them vertically by the side of the Nascom 1. There my problems
began... Firstly the modulator and PAL encoder board is not screened at
all, and picks up the timing pulses from the graphics generation board,
resulting in a crosshatch pattern being visible on the screen. This I
partially solved by careful adjustment of the modulator trimmer
capacitor, and by altering the video drive resistor to lower the black
Software has been relatively easy to write in machine code and Basic.
Some amazing and beautiful displays are possible.
I would recommend the kit to anyone thinking of CHEAP colour’ graphics,
as it is, in my opinion, excellent value for money. The only
disappointment being that the modulator does not give as good
definition and clarity as that of a screened modulator such as the
Aztec colour module.
One last word; as the software is designed for optimum use of colour
and graphics in 4 pixels per character, and Nascom’s graphics option
being 6 pixels per character, using the SET, RESET and POINT commands
in the 8K Basic gives some very peculiar results. However, a SET
routine using the USR(0) command is easy enough to write.
review David Hunt
mentioned that by writing your
own control software the Imp
becomes capable of all sorts
of special tasks. Here is an
example of some work done by
Graham Rounce. The program is