80-Bus News


July–August 1983 · Volume 2 · Issue 4

Page 9 of 55

to allow this feature to be used to the best advantage. A further possible ommission is that room was not found for a binary adder on the board as this could then allow very high speed colour ‘rotates’ to take place a la BBC computer. Perhaps it could be argued that the provision of this feature would be more of a gimmick than useful.

Another useful feature is the provision for placing two RAM planes ‘side by side’, allowing the use of two colours in a very high res mode of 784 x 256. Use is made of this feature when the AVC is used as a terminal with Nascom’s CP/M to allow the card to be used as an 80 x 25 text display with high res. graphics thrown in. The only snag with this mode is that the 80 x 25 display is effectively bit mapped. This means that the characters have to be looked up in a table and displayed as graphics. Fine so far, but when it comes to scrolling, it means that 32K of video RAM has to be scrolled to remap the characters in their new positions. This makes scrolling rather slow.

Port controlled provision is provided for the routing of the normal Nascom video through the AVC outputs, allowing the use of one common display monitor. The 48 x 16 normal Nascom display is suited to a colour monitor. But this approach gets a little complicated when debugging programs as it is often useful to have the normal Nascom display displaying say, counters, etc, within a program whilst the colour display is constructing a picture.

The Climax Card.

The Climax card is available in two versions, Version A provides modulated RF output using a high quality wide bandwidth modulator and PAL composite video with mixed syncs at £199.00. Version B provides modulated RF and composite PAL as before, and also analogue RGB outputs at £220.00. In neither case are separate syncs provided and we had to extract a separate composite sync signal from elsewhere on the card to make the Kaga montiors lock. Note that the outputs are analogue as the Climax card is capable of full and half saturation colours. Be careful when selecting a colour monitor for use with the Climax, as most cheaper monitors are logic inputs only, and the full benefit of the half saturation colours will be lost, displaying either black or full saturation colour. The only moderately priced monitor found to be suitable for the Climax RGB drive is the KAGA Vision-I monitor which, whilst not quoted as being analogue, worked extremely well.

The Climax uses 64K by four bits of RAM and is under command of the Thompson colour controller chip which gives 256 x 256 resolution in eight fully saturated colours and eight half saturation colours. The screen display is totally square, leaving black margins at either side of the screen.

The card is port addressed using seventeen ports from C0H to D0H inclusive. This makes the card greedy of port allocations, but exceptionally easy to understand. Single and multibyte instructions are passed to the various controller registers to perform a number of different functions directly, but software generation of some of the more complex functions is required.


The Pluto Card.

The Pluto card is equally suited to either Nascom or Gemini machines. The card is provided with the NASIO decode signal, although this is only partially decoded. No system specific software is included, so there is no problem from the software point of view. Being totally port addressed no provision has to be made within the memory map.

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