When I decided I wanted to code on the 6502 again and realized I didn't have a physical retro platform I could use, I contemplated building a real HW 6502-system. I certainly have the skills to do it, but I dislike the work involved. Soldering is fun for just a short while before it gets tedious :)

A good compromise between HW, SW and mechanics I came up with involves emulating most of the system components in software on small microcontrollers.

Generation 1 of the system ran on a cheap Blue Pill that can use the Arduino framework. The 6502-emulator I used was a slightly modified version of fake6502 by Mike Chambers.
It took very little effort to get it working, and I immediately implemented ehBasic which is extremely nice to use as a debug- and test-environment of the emulated HW-components.
The problem with the Blue Pill is limited RAM, only 20kb, and I wanted at least a 128kb bank switched 6502 system in the end. Inspired by Shane Goughs TGL6502 I tried to get around this by using an SPI RAM-memory @20MHz, but the memory bandwidth meant a 6502 speed of only around 0.5MHz. This was when the memory was random-accessed, and going to sequential accessed memory increased the bandwidth to just less than 2MHz, but varied wildly depending on work done. Clearly not ideal, even if the bread-boarding of an SPI-RAM is VERY simple. Oh well, I'd wanted to try this anyway...