80-Bus News

was port addressed using the TI colour video controller. This controller features ‘sprites’, which are preformed patterns which can be manipulated with incredible speed once set up. I have yet to see one of these cards working, but I have heard dark mutterings from various directions about the damn thing not doing what was expected of it.

Some time ago a sample card was shipped down from Edinburgh University for a group of dealers to offer their opinions. Very few details were supplied with it, except that it was a port addressed 8″ x 8″ card, the resolution was something like 350 x 256, but its most interesting feature was that the demo displayed amongst other things a test card with a 16 step grey scale wedge. Some time during the day the card (which was after all a prototype) crashed and at the end of the day it was shipped back to Edinburgh. That is the last that has been heard of it – a pity, a could be a contender in the colour card stakes.

As I said earlier, I can not recall anything about the A N Other card which was discussed at the East Grinstead meet.

I have also seen the circuits and chat about a Dutch designed colour card which was published in the Dutch equivalent of ‘Nascom News’. This one is similar to the Climax card except it uses the 256 x 512 version of the video controller and has an AY-3-8910 sound chip on it as well.

The Comparative Review.

Of those listed above only three are in serious production, the Pluto, the Nascom and the Climax. I have been having fun (or tearing what’s left of my hair out) with these. I propose to review the features of each of the cards under different subheadings. Where appropriate I shall digress.

The Monitors.

For the first digression, and before getting on with the review, let’s have a have a look at the display requirements. Colour monitors are not cheap, and the domestic colour TV appears at first sight to a be viable alternative. Unfortunately, the easiest entry into the domestic TV is the RF input, which just happens to be the most unsatisfactory. Some TV’s notably of European origin, Normende, Grundig, etc, have composite PAL inputs on the back for connecting Video Cassette recorders, which would be satisfactory with the Climax card. Many TV’s have RGB inputs for the inclusion of Teletext panels if you know where to look, but it is highly dangerous to assume that these would make a safe connection as most colour TV’s use chassis live to one side of the mains, and connection here is a quick way of taking a ride to the mortuary. So unless the TV has the right connections on the back, or unless you are thoroughly aware of what you are about, DO NOT make connections inside the domestic TV set.

The Nascom and Pluto cards do not have RF outputs on the grounds that the resolution is too high for the domestic TV, certainly true in the case of the Pluto, perahps arguable in the case of the Nascom. The Climax card is fitted with a modulator for connection into a TV. Even so, the results from a TV are very much inferior to the results from even a modest colour monitor.

So to the choice of monitors. These are normally available in three resolutions and with two types of input, analogue and logic. Resolution first. Not all manufacturers make all types, but the information can usually be extracted from the data sheets, albeit, sometimes disguised as something else. Resolution is usually measured in vertical lines. Not to be confused with the number of horizontal lines on the display. Vertical line resolution is taken as the maximum total number of vertical black/​white lines the display is capable of resolving across its face, and is a function of the fineness of the