Colour and your computer – the choices.
by D.R. Hunt
The Colour Cards.
Some time ago I was asked to give a talk at the East Grinstead
Computer Club. I hope a good evening was had by all despite the rambling
nature of my chat. I know I enjoyed myself, apart from the fundamental mistake
that when I agreed to go, I had firmly fixed in my mind that East Grinstead
was reasonably local, being somewhere north of Finchley, instead of being half
way to Eastbourne. One of the things to come out of the evening was what was
my opinion of all the colour cards around? When we totted them up we found
there were seven:
The Winchester Technology Colour card
The Nascom AVC
The R & E W colour card
The Edinburgh University colour card
A N other colour card.
There were definitely seven, but for the life of me, I can not now recall
whose the last one was. My opinions weren’t much use at that time either, as I
had only gained experience of one of the cards, and hadn’t even seen most of
them in action.
Since then, I have to some degree rectified my lack of experience of
colour cards, having seen all but one, and played with most, three have
occupied some considerable time over the last couple of months. When I wrote a
preliminary note about the Nascom colour card some issues back, I was
sceptical as to the uses a colour card could be put. I’m afraid I still remain
unconvinced, and I think it would take a radical change in my thinking and
uses of my computer to persuade me that any colour card should be given a home
in my computer box.
Now lets have a quick look at each card. The Winchester Technology
Colour 8″ x 8″ memory mapped card was by far the earliest and used the Mullard
Teletext controller chip set. This made it fully Prestel and Ceefax
compatible, but not really high resolution. The card is no longer
manufactured, which is a pity with the growing interest in Prestel and Ceefax
compatibility, it could be a big sales point these days to have a range of
computers which are Prestel and Ceefax compatible.
Next to arrive was the
card in its various forms. Again an 8″ x
8″ card but this time port addressed. Possibly the fastest and most powerful,
certainly the most expensive and the highest resolution. This card uses an on
board 16 bit (8088) processor and carries its own bus structure for even
further, mind blowing expansion.
After a long wait came the Nascom AVC, an 8″ x 10″ card built round a
video controller chip.
It uses page mode memory mapping to address it,
and features comfortably high resolution and a nice range of software bolt-ons
to go with it.
Then, quite recently, came the Climax Computers card. An 8″ x 8″ card
built round the Thompson Video controller chip and port addressed. Lower in
resolution than either the Pluto or the Nascom, but with limited grey scaling
and some of the best explained software primitives I have yet to see.
R & E W, the magazine sponsored by Ambit International, the components
people, entered the field by publishing an article on a colour card which was
then made available as a kit. This one was either a 10″ or 12″ x 8″ card and