Here's a roundup of eurorack modules for chiptune sounds. SID GUTS by ALM is built for original Commodore 64 chips. The Analog Bytes POKEY.synth has the Atari POKEY chip on board. Other eurorack modules like the Atari Punk Console by Synthrotek, the Ataraxic Translatron by Noise Engineering and Edges by Mutable Instruments produce the lo-fi digital shift register sound using similar circuitry.
SID GUTS
SID GUTS by ALM can host a single Commodore 64 SID voice, featuring 3 wavetable oscillators, an analogue (!) multimode filter, ADSR, variable pulsewidth, oscillator sync and ring modulation. The SID GUTS is like a modular breakout box: you buy it without the SID chip. ALM actually recommend to insert the updated SwinSID which draws less current. For more info check the manual. Jahtari has a C64 history and an interview with the developer of the SID which btw doesn't have 8-bit guts [that was a purist 8-bithead disclaimer].
ALM003 - SID GUTS from ALM on Vimeo.
POKEY.synth
The original Atari POKEY chip is implemented in the POKEY.synth module in a very versatile way, extending the pitch range and adding extra tricks like the lo freq triggers, the hi pass filter and the bitcrushing aux input. For more info check the blog and manual. A 2A03 (Nintendo NES) based module is in planning stage. Awesome!
Ataraxic Translatron
The Ataraxic Translatron by Eurorack newcomer Noise Engineering is a small but versatile lo-bitrate digital oscillator. It's not based on an original Atari soundchip like the POKEY or 2600 TIA but who cares, it sounds noisy and lo-fi enough. Noise Engineering say the chip in the 4HP wide module "is similar to those used in the first generation of home video game consoles such as the Atari VCS as well as many other classic arcade games." Clock mode is a really nice extra.
Zorlon Cannon MKII
The new Zorlon Cannon is described by The Harvestman as a "Dual-clock LFSR battery with external inputs and mixers. Suitable for the generation of random gates, digital noise, and pitched tones in the same manner as the classic Atari "POKEY" sound chip." The top section is optimized for gates, bottom section is better for audio. The Zorlon Cannon has variable bit length and lots of advanced options. It can sound both clean and dirty and it looks great, like all Harvestman modules. The videos show the older Zorlon Cannon MKI.
Edges
The Edges is a 4 voice lo-bitrate oscillator by Mutable instruments, who say that "its architecture is loosely based on classic 8-bit console soundchips". The first 3 channels are straight up lo-fi square/pulse oscillators. Channel 4 CV input can be used as a PWM CV for channels 1 to 3, with a 120° dephasing between each channel. Channel 2 can be hardsynced to channel 1. Channel 2 and 3 are also equipped with a XOR ring-modulator. Channel 4 uses a naked 12-bit DAC to create lo-fi sounds at 48kHz sample rate. Edges has more tricks up its sleeve, like a semitone quantizer and an 8-step mini sequencer. Interesting.
Atari Punk Console
The Atari Punk Console is a classic design, often sold as a kit but you can buy prefab modules from Synthrotek. This one is very basic compared to the others, but hey.. punk is about keeping it simple.
Doepfer A-117
The humble but versatile Doepfer A-117 Digital Noise / 808 sound source also has a simple linear feedback shift register. It's not really useful for 8-bit melodies but it does have the shift register noise.
vcNOIZ
The hexinverter vcNoiz is based on the Roland TR 909 noise generator. Like the A-117 it's a shift register-style noise source. It has exponential 1v/oct pitch tracking ~ quite unique for a noise generator ~ and this makes it more versatile than the A-117. You could even mix vcNOIZ output with a square wave melodic sound.
