Retro demo scene coding - ZX Spectrum 101

The Sinclair ZX Spectrum was released to the world in 1982. Not even the most powerful computer when launched, you can imagine how limited a platform it is by today's standards. With an awkwardly low screen resolution, a colour palette straight out of coder-art-school, a slow CPU and not even any custom hardware to make up for it, you would be forgiven for wondering how it ever survived. But survive it did, spawning several hardware updates and selling over 5 million units in the ten years that it lived. If the demoscene teaches us anything it's that limitations breed creativity. So it should come as no surprise to find that, along with other contemporary computers like the C64, the Spectrum branch of the demoscene is alive and well in 2018. In this seminar I will introduce you to the hardware of the ZX Spectrum 128 - the standard ZX demoscene platform. We will look at some techniques to coax 50hz music and visuals out of a machine that, in all honesty, barely has the CPU power to do so. I will show how these techniques can be built upon to make a modern Spectrum demo and I will provide the full source code and toolchain for a demo engine to start you off on your ZX demoscene journey.

Paul Grenfell has been a software developer since he was 8, growing up in the home computer boom of the 1980's. In the late 1990's while working in the UK games industry he got involved with the demoscene and never left. He has released a number of demoscene projects under the handle evilpaul for his demo group Ate Bit.

Author: Paul Greenfell

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