RWW and JRG visited Computer Special Systems at DEC to see the colour monitor CPS-8OO1 which DEC attach to a PDP15. We also saw a VT30 and were told about the VT31, both of which require a PDP11. We spoke to Stuart Haughton (Applications Engineer in Special Systems). There are brochures on all three systems in JRG's office.
The CPS-8001 is an arbitrary vector display with 4 colours manufactured by CPS (of California) which can be driven by a modified VT15. It includes a single electron gun and, next to the screen, 2 phosphor layers, red and green. The lowest voltage 9kV excites the red layer and the highest 16kV excites the green. The other two voltages selected by the VT15 are intermediate and produce orange or yellow. The colour can be changed in 15sec. There are 8 programmable intensities for each colour. Stuart Haughton could not say what would be the effect of drawing a line twice with different colours. The answer would probably depend on the respective intensities and the time interval between the two strikes.
DEC make the modification to a standard VT15 and the colour change is effected by a display file parameter order using previously spare bits (2 to specify colour and presumably 1 to enable bit). All other display orders are the same.
We saw the colour monitor working, using a modified "little pictures". The colour was reasonably good, although a line drawn once is rather lacking in contrast. The lines were not meeting properly, even though it was going out to a customer next day. There is also a slight shift when the colour changes and one of the "little pictures" subprograms manifests this.
In spite of the criticisms of detail, it is attractive to see the colour combined with the responsiveness of the traditional refreshed type display. The phosphor is fast, there is no apparent ghosting (the specification says it is a P22). Because of this though, the possible amount of flicker-free information is small.
A light-pen is optional. There are problems because the light-pen cells must be sensitive to the particular narrow bandwidth of light being emitted. However, if (and only if) the light-pen is held almost touching the tube face, the "little pictures" light-pen test works as fast as on the VT04.
RRE have more than one, Mullard Laboratories have one and there are about 20 in the USA.
The monitor must be bought from CPS, not through DEC, price £10,000. The former British agents for CPS have been dismissed and a new agency is being established with Munzig International Inc, 9 Windsor Road, Slough, Bucks (Slough 34003). The level of support via Munzig is not known at the moment.
The delivery on DEC's part would be 4-5 months. A new VT15 with the modification and without the CPS is £6,000. The cost of a modification to an existing VT15 would be £3,000. Stuart Haughton was not able to say wwhther the CPS could be added to a VT04 on the same VT15 and could not give a price. The light-pen is £4,000 and a tracker ball is £1,200.
The VT30 is controlled by a PDP11 and can control a standard 625-line colour monitor (in fact more than one monitor can be served but only one picture can be put out). There is a variant of the VT30 which serves 4 black and white monitors with different pictures.
The resolution is 512 × 288 and the colour set is on the end of a coaxial cable, which could be up to 500 metres long.
The VT30 contains the definitions of 128 character shapes defined on an n × n dot matrix (n can be 6 or 8 depending on which you buy). Character shapes can be redefined by software.
The picture is made up of a sequence of picture elements each consisting of a character number and 2 colours, foreground and background. There are 8 colours altogether and a simple repetition facility.
The basic VT30 only has a store for the characters, so the PDP11 has to scan the picture at 50 frames/sec. If the VT30 includes a picture store, the PDP11 only has to send alterations and the VT30 refreshes.
The VT30 seems useful for low resolution areas of colour at low cost (for instance a map of France with supply routes and referendum results on ITV). Its line-drawing ability is limited, although a map of the Swedish underground was quite interesting. To draw a vertical line requires a character definition of a vertical line.
Prices and models (excluding PDP11, UNIBUS and a colour monitor)
VT30A character store only 6×6 character grid £2000 VT30B character store only 8×8 character grid £2000 VT30C character and picture store 6×6 character grid £3000 VT30D character and picture store 8×8 character grid £3000
The VT31 is also controlled by a PDP11 and controls a standard 625-line colour monitor. Every point on the 512 × 288 raster can be separately specified with one of 8 colours so its line-drawing capability is more flexible than that of the VT30. We did not see one of these. The first one, is going to a group in Harwell at the end of this year. Stuart Haughton said he would inform us which group this is. Price for the VT31 itself is £8,000.
