I've also been working on my Acorn System 1 storage expansion card; and I needed a working EPROM/EEPROM programmer so I could flash an EEPROM that contains the boards memory map.
The CPU simulator on the right is designed to allow me to wiggle all the Address, Data and Control signals. It makes it really easy to set up known signal patterns to a project under test, and then poke around with a scope lead and see what's going on. It connects to the breadboard via a ribbon cable which can be removed, allowing the project to be hooked to a special expansion card that plugs into the computers backplane.
There will be a full breakdown of how this board works (assuming it does work) soon, but in brief the board contains RAM and EEPROM which are both broken into pages. When completed the card will occupy around 56K of space in the memory map, but will contain around 8Mb of EEPROM/RAM that can be brought in and out of the map as pages.
The two, two digit LED displays on the left show the page numbers for the RAM and EEPROM. The Two digit display at the tope of the board shows the offset that is applied to the memory to allow access to the right page.
All the buffering and decoding logic, as well as some debugging displays/leds etc are on that breadboard including a flash memory that is used to calculate the offsets into the EEPROM/RAMs. The only two components that are missing are the actual EEPROM and RAM chips. They get added next and then I'll find out if this actually works.