The Sinclair ZX80 is a low cost home computer, launched in 1980 with a price tag of £99, considerably cheaper than it’s contemporary counterparts. How did they do that? Well, the first thing to know about the ZX80 is that it’s main job is not to run your code. That’s very much a side task. The thing it spends most of its time doing is drawing a picture on the TV screen. And it does that be executing mainly NOP instructions.
Unlike most other computers of its era, it doesn’t have a video chip. It doesn’t have any custom chips in fact. There is a Z80 CPU, a 4K ROM chip, and two 1K x 4 bit RAM chips, and seventeen 74 series TTL chips, and that’s it.
Follow the details on how this was all accomplished in this blog post.
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