My article on how to upgrade your 8-bit Atari. I describe how to mount three extensions: Ultimate 1MB (additional 1024kB RAM and many other features), Simple Stereo and Sophia Rev.C (digital video output via DVI). http://en.devzine.pl/2019/09/23/how-to-upgrade-your-atari-with-ultimate-1mb-stereo-and-sophia-dvi/

Here is my first retro-tutorial: "DIY: Improved SDrive-MAX - a hardware disk drive/tape recorder emulator for Atari 8-bit computers based on Arduino."  http://en.devzine.pl/2019/05/08/how-to-build-sdrive-max/