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 syne 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
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.