Welcome to the Sinclair LC3

Artists impression of the LC3

The Sinclair LC3 is an unreleased prototype produced post Spectrum. The plan was to produce a rock bottom price machine - even compared to the Spectrum. Hence "Low Cost Colour Computer" 

It did exist - there seems to be little question of this (unlike Loki / SuperSpectrum) probably as a breadboard design or maybe a little further.

The picture shows what it was thought to look like, basically a microdrive cartridge (probably slightly bigger as it would barely fit in a microdrive) with a slot in the front for a cartridge.

The image is courtesy of the excellent "Lairds Lair" youtube channel, there is a video about this machine here.  Another good article is in the Register.

I have contacted (or tried to) Martin Brennan and Steve Berry with some ideas and specific questions. I suspect they get a fair few regarding Sinclair machines, but they are more vagaries like "send me anything you have". To date, neither have replied ; both are busy men and as I said probably get pestered a lot.

You never know though. I did this with the Microvision, with the same sort of idea - I had more information for that - the CPU (TMS1100/Intel8021) and the Harris LCD chip ; Dan Boris had already worked out the PCB. So I'm merrily coding away, and I get contacted by decap wizard Sean Riddle saying he's got some ROM dumps of Microvision cartridges. So it went from a theoretical project to a real one running real code. 

One thing I've learnt doing this for 25 years is, if you don't ask you don't get, and sometimes what you *do* get is amazing. That's a story for a later date .... but a hell of a story.

To start with, I will look at what is known, what is claimed, what might be, and what we can guess at (in an educated fashion....)