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Questions tagged [zx81]

For questions about the Sinclair ZX81.

5
votes
2answers
380 views

Membrane keyboard robustness

Some early computers used a membrane keyboard (ZX80, ZX81, Atari 400), or semi-membrane with minimal keys (ZX Spectrum). This is because it was cheaper than a mechanical keyboard. Intuitively I would ...
13
votes
1answer
1k views

How do high-resolution graphics work on the ZX81?

The ZX81 has a display file which is treated rather like a serial file. And the CPU generates addresses which the ULA uses to look up the characters' bitmaps from the ROM (Yes, I know the actual ...