Hardware Development Kit
The Hardware Development Kit was a ‘hobbyists hardware kit’ for the Coupé. Half the circuitry provided the user with parallel I/O ports, and the other half was The Kaleidoscope which enabled manipulation of the RGB video signals to give a palette of theoretically 32,768 colours with 2,048 per screen with line interrupts.
The Hardware Development Kit was released by Search: “SamCo” as a kit to solder up for £29.99.
It was also sold built up with just the Kaleidoscope circuitry (no I/O components) and marketed separately as The Kaleidoscope which retailed for £34.99 and housed in the usual white interface box.
The colour changing circuitry was just 1 extra chip on top of the address decoding logic, 8 resistors and 3 transistors forming 3 simple Resistor DACs which drove the transistors to pull down on the red, green and blue video signals.
It was a complete bodge.
What the kaleidoscope did was pull down the RGB video signals generated by the Sam as normal (by darkening the output by varying amounts of red, green, blue - set with an OUT command to the kaleidoscope port) so it technically produced 256 tinted shades of the original colours - in total 32768 shades, but could they be used in a proper fashion - nope!
So whatever value of shading the kaleidoscope was set to would affect all the colours on screen. There was no real way to use it all, could you have individually shaded pixels - nope again!
At most, you could write code to tint horizontal groups of 16 pixels at a time… but for all 192 scanlines you would be using all the CPU time and even effectively tinting 16 pixel blocks that wouldn’t really let you achieve any decent graphical effects, plus 62% of all the CPU time is being used.
In all, a waste of time, it couldn't be utilised in any useable way at all, therefore no software attempted to used it.
And some more:
The Kaleidoscope changes the red/green/blue voltage levels, which in turn feed the MC1377 Composite Video generator. The subtle changes the Kaleidoscope make will be seen no matter what video signal you use - RGB, Comp. Vid or UHF.
In Your Sinclair July 1992 Issue 79.
“The Forgotten Artifacts of SAM - The Kaleidoscope” a 7 page feature in Sam Revival issue 15 (May/June 2006).