Hello DropCheck, I’m the guy (not gal) you were Private Messaging and it is your lucky day. Attached are pictures of the original pencil drawn schematics of the parallel buffer and the ink velum of the serial buffer. It’s a miracle that I still have these and was able to find them. My name is Richard Taylor and I was the warranty repair department, shipping department, prototype builder, janitor, etc.. at DDC (Digital Devices Corporation) while I was going to Georgia Tech in 1984/85. Paul Nodwell was the Engineer/part owner and we have not heard from him since we closed the doors. Oooooh the stories I could tell about the good ol’ days at DDC. It was an incredible experience for an aspiring young Engineer. My first two computers were a 400 and 2600, so Atari has been a huge part of my life. I love seeing old equipment resurrected and will help where I can. I’ll dig in to my boxes of stuff and see if I can revive some damaged brain cells, but I remember the original APEFace was a Z8601 with a separate EPROM. This later evolved into a custom CPU with the program burned in to an internal ROM. The original printer buffer never had a separate EPROM. I spoke with the other engineer years ago and he said there is a way to bypass the internal ROM and use it as a standalone 8601, but can’t remember how and have not heard from him in 20+ years. I still have 1000’s of these old chips, boards, and components. Richard