Plan C | Making & Programming a Nano Swinsid-b @Plan-C | Uploaded September 2019 | Updated October 2024, 7 hours ago.
I followed Tolaemon's excellent tutorial to make a few SID replacements for some C64s. I used a cheap USBASP programmer and ProgISP instead of an expensive AVR programmer and Atmel Studio. Bonus drunk footage of un-bricking a mis-programmed Atmega using a TL866ii at the end

Tolaemon's Howto: (includes firmwares, gerbers etc): tolaemon.com/nss/index.htm

Software used to program Atmega: Progisp: noobieelectronic.blogspot.com/2018/01/how-to-install-progisp-on-pc.html

USBASP Drivers: https://protostack.com.au/2015/01/usb

AVR Fuse Calculator: engbedded.com/fusecalc

Good Luck All