ZX Spectrum System Tour: Sound

3 hours ago

The ZX Spectrum offers two sound options: a 1-bit beeper and an AY-3-8910 synthesizer chip.
The 1-bit beeper can be controlled via BIOS routine at $03B5 using frequency and duration codes derived from formulas.
A direct beeper routine with precise timing avoids branch timing issues using JP instructions instead of JR.
The direct beeper method suffers from CPU wait states due to video memory access, requiring code relocation or workarounds.
The AY-3-8910 chip on Spectrum 128 is programmed via ports $FFFD and $BFFD with a clock of 3.5469 MHz.
The beeper is best for short sound effects, while the AY-3 chip can handle more complex music and ambient sounds.

A 16-bit serial homebrew CPU was built using only 8 ICs, including memory and clock, achieving Turing completeness.
The CPU uses a single EPROM as both control state machine and 1-bit ALU, with two serial SRAMs and one serial FLASH.
It executes around 12,000 instructions per second at up to 10 MHz, capable of streaming video on a Nokia 5110 LCD at ~10 FPS.

<antirez>7 days ago

The Raspberry Pico is a well-made, durable chip with a ton of features, including state machines for GPIOs, and its lack of connectivity is resolved by the W variant.
The chip is well supported by MicroPython and the C SDK, though the build system is overcomplicated for small programs.
To generate sound without a DAC, PWM can be used with a high frequency and varying duty cycles to approximate different voltage levels.

PartialString uses finite-difference time-domain (FDTD) to simulate a plucked string by solving the 1D wave equation in real time.
The string is represented as a list of displacements; lower notes require longer strings with more points.
Controls include excitation position and shape (velocity-sensitive), LFO-swept pickup position, adjustable decay time, and piano-like dampers.

The Intel 8087 coprocessor accelerated floating-point calculations up to 100 times on IBM PCs using microcoded algorithms.
The chip's microcode ROM contains 1648 micro-instructions that control internal operations like data movement and arithmetic.
The microcode engine supports conditional jumps, subroutine calls, and returns based on 49 different conditions.

The author dislikes the harsh beep of microwaves and tries to silence it by opening the door before it sounds.
Microwave beeps are produced by a cheap piezoelectric buzzer, which can only vary frequency and duration.
Sound designers Joel Corelitz and Colin Coogan from Starling created improved sounds using only software changes on existing hardware, such as trills and frequency sweeps.

A 16-bit serial homebrew CPU was built using only 8 ICs, including memory and clock, achieving Turing completeness.
The CPU uses a single EPROM as both control state machine and 1-bit ALU, with two serial SRAMs and one serial FLASH.
It executes around 12,000 instructions per second at up to 10 MHz, capable of streaming video on a Nokia 5110 LCD at ~10 FPS.

<antirez>7 days ago

The Raspberry Pico is a well-made, durable chip with a ton of features, including state machines for GPIOs, and its lack of connectivity is resolved by the W variant.
The chip is well supported by MicroPython and the C SDK, though the build system is overcomplicated for small programs.
To generate sound without a DAC, PWM can be used with a high frequency and varying duty cycles to approximate different voltage levels.

PartialString uses finite-difference time-domain (FDTD) to simulate a plucked string by solving the 1D wave equation in real time.
The string is represented as a list of displacements; lower notes require longer strings with more points.
Controls include excitation position and shape (velocity-sensitive), LFO-swept pickup position, adjustable decay time, and piano-like dampers.

The Intel 8087 coprocessor accelerated floating-point calculations up to 100 times on IBM PCs using microcoded algorithms.
The chip's microcode ROM contains 1648 micro-instructions that control internal operations like data movement and arithmetic.
The microcode engine supports conditional jumps, subroutine calls, and returns based on 49 different conditions.

The author dislikes the harsh beep of microwaves and tries to silence it by opening the door before it sounds.
Microwave beeps are produced by a cheap piezoelectric buzzer, which can only vary frequency and duration.
Sound designers Joel Corelitz and Colin Coogan from Starling created improved sounds using only software changes on existing hardware, such as trills and frequency sweeps.

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