Former Microsoft engineer Plummer has developed a custom RAM card for the 1970s PDP-11 computer. The project aims to provide 4 MB of memory, utilizing a Lattice MachXO2 FPGA as a controller alongside four 1 MB ISSI memory chips.
The engineer utilized ChatGPT and the EasyEDA circuit simulator to assist with the design process. The hardware was built as a standalone card for the Q-Bus, tested alongside an M8190 CPU board on a backplane.
During development, the project faced challenges with FPGA flash programming and memory bus logic. The PDP-11 architecture requires specific word-based access, which initially resulted in the system only recognizing half of the intended memory capacity.
Plummer also experimented with modern interfaces, including a QBone DEC board equipped with a Beaglebone Black. This setup allows for software-based memory implementation, serving as an alternative to the custom hardware approach.
