Quazar's SID Interface Board Brings Commodore 64 Audio to the RC2014 and Compatible Computers

Retrocomputing enthusiast Colin 'Quazar' Piggot has released an unusual add-on for the RC2014 modular vintage-themed computer: a board that allows it to interface with a MOS Technologies SID audio chip, as made famous by the Commodore 64.

"I first produced a SID sound chip interface back in 2003 for the Z80 based 'SAM Coupé' computer," Piggot explains. "This all stemmed from my own small pet projects exploring old forms of computer sound — with its unique sound, the SID sound chip remains very popular with computer audiophiles to this day. Adapting the interface to work with modern Z80 based systems, in this case the RC2014 and similar compatibles which share the RC2014 I/O bus, was a logical step to follow."

"This interface connects to a standard RC2014 slot and allows the Z80 to write to the registers of the SID chip. To assist timing I've also added an interrupt generator which can be set to generate approximately 50/60/100Hz interrupts, timed to match the frame rate of the Commodore 64. There are jumpers on the interface to allow the base I/O address to be configured, with the default set to 0x54."

While the interface takes care of physically connecting the RC2014 to the SID chip — complete with a choice of configuring the board for the SID 6581 or the less-popular but more common SID 8580, or using an adapter board to chop and change between the two — there's still the thorny issue of software. "Currently there's no specific software for the RC2014 to drive the interface, so please don't purchase the interface and think you'll be playing SID music within seconds," Piggot notes.

"Programming information with regards to how to write to the SID's registers and enabling the interrupt controller is covered in the guide with the interface along with some Z80 routines. There is Z80 code on GitHub (as originally written for the Z80 based SAM Coupe) for emulating the C64's 6510 CPU to play .sid files, someone could rise to the challenge of porting that to the RC2014!"

The interface is now available on Tindie for $65.79; no SID chip is supplied, but the board has proven compatible with both original SID chips and modern recreations including the SwinSID family and ARMSID.