The SID Homepage — The creation of the SID chip (Christer Rindeblad)

A short column by Christer Rindeblad, reprinted on the sid-homepage, on how the sid came to be, with three quotes from bob-yannes. Its dates (project start, team, months of development) are the ones the wiki has for the chip's origin.

Key claims#

• "Project C64" was first discussed at Commodore in January 1981 as a game computer; during the project it became "a true home computer" (commodore-64). Two groups worked on it: one for the graphics chip, one for the SID ("Sound Interface Device").
• Work on the SID began in spring 1981 under Robert Yannes, "a young engineer who had been responsible for the design behind the VIC-20"; his team was himself, two technicians and a CAD operator. Yannes: "I had worked with synthesizers and I wanted a chip like those in a synthesizer." Nobody in the team knew how to carry out the project; "Apart from the basic research, that I'd been doing since high school, the actual development of the SID took just 4–5 months."
• The chip's quality relative to game-console sound: precise frequency control and an independent envelope generator per voice (adsr-envelope).
• A note-to-frequency table was originally built in and later removed as too expensive (Yannes says the same in s-sidmusic-yannes-interview).
• The specification "written while the chip was developed accidentally got incorrect", so "the real capacity of the SID-chip is not fully known even today — not even by its constructors"; the column gives as an example that "the documentation states that the chip can perform a logical AND on different waveforms", and "another error is in the filter-function".
• Yannes on the filter: "The filter was the last feature we added in, and there was no time to make it perfect … Computer simulations told us the filter wouldn't work out very well. And it didn't. I had no chance to correct the errors."

Practical takeaways#

Dates for the chip's origin (January 1981 project, spring 1981 start, 4–5 months of design) and the reminder that the official spec was written before the silicon and is wrong in places — the reason so much SID knowledge is empirical.

Notable quotes#

"Apart from the basic research, that I'd been doing since high school, the actual development of the SID took just 4–5 months."

Relevance to the wiki#

Origin dates for sid and bob-yannes; a second account of the filter's failure and of the inaccurate spec. Note the contradiction on the AND-ing of waveforms: this column calls it a documentation error, while Yannes (1996) and the datasheet describe the combination as a real logical AND of the waveform bits.

Pages touched#

sid · bob-yannes · sid-homepage · commodore-64 · adsr-envelope · c64-programmers-reference-guide