Some time ago I attempted to create an Apple 1 replica based around Vince Briel's earliest rendition of Replica 1. Mistakes were made, and I never did get the unit working. I know for sure that I blew the 65C02 by piping in 5v where is wasn't supposed to, so I dropped the project for a while.
I've just started up again with a batch of fresh parts. This time I'll be prototyping on a breadboard, and I'm basing it around the second generation Replica 1 Plus that Mr Briel released some time ago.
It's a shame that these kits aren't being sold anymore, as it was a good budget alternative compared to the very nice Mimeo and Newton replicas that are out there. The only other budget replica (that I am aware of) is the L-Star. But rather than buying a kit, I'm determined to try and put this together on my own, on a breadboard first and, if all goes well, on a prototyping PCB. The breadboard version will leave off the expansion port and edge connector, as well as the ASCII keyboard, for the sake of simplicity. The PCB version should include these though.
Apart from stroking my ego, I want to learn more about the low-level fundamentals of computing. I learnt a lot from my previous attempt, and am hoping to learn even more this time around.
I have put together a parts list on Mouser if anyone is interested, minus a few things like the edge connector, expansion port, and the ROMs. Last time I had someone burn me a ROM; this time I've ordered blank ROMs on eBay, a programmer and an eraser to do it all myself. This has pushed the cost up. Additionally my shopping list included a Prop Plug to program the Propeller chip. I'll be using Mr Briel's latest (and last?) Propeller firmware, and the latest version of the 16 kilobyte ROM image that includes the Monitor, Krusader and BASIC.
This probably won't work, I don't really have faith in my abilities to follow the schematics and not make fatal mistakes. But if I go slow and test everything three times over, I might just get a working Apple 1 replica out of all this.
Below you can see the address and data buses for the ROM (middle) and the RAM (right). I'm still waiting on the ROM programmer from China so I'm not rushing to get anything finished at this point.