<snip> Having an 18-bit Unibus interface for the KS10 is a great idea. You could easily put enough RAM on the board to emulate several Massbus disk drives and save the disk images on flash. Last year I made a Posibus Peripheral Emulator with an Actel SmartFusion FPGA/ARM http://www.ricomputermuseum.org/Home/equipment/pdp-8-l/making-a-posibus-per… I started with an Emcraft SOM module, used the free FPGA tool chain from Actel, and the FPGA and uC Linux image from Emcraft. Linux was running on the SOM when it was first powered up. http://www.emcraft.com/products/255 All I needed to to was make an interface board from the 3.3V logic in the FPGA to the Posibus in the PDP-8/L. My idea was to put the time sensitive logic in the FPGA and do everything else with a Linux device driver and application. You could do the same and use something like an M9014 module to connect to the Unibus. Once the circuit was debugged you could make a PCB that plugged directly into the Unibus and had a socket for the FPGA SOM. Since all of the Unibus logic is in the FPGA the single board could respond to many Unibus addresses and then emulate multiple peripherals at the same time. With a little FPGA logic change, and a bit of coding, you could run SIMH on the ARM in the FPGA and then emulate just about any CPU. -- Michael Thompson