I just finished the layout for the MCL86jr, which is a small board which can replace the 8088 CPU in the IBM PCjr. It uses my MCL86 CPU core with a “minimum” mode BIU (Bus Interface Unit) and is implemented in a Xilinx Spartan-6 FPGA. The board contains a 512KB Static RAM which can bring the PCjr’s total RAM to 640KB or can be used to mirror and accelerate the BIOS ROM or even load PCJr cartridge images!
The MCL86 core can be used in “cycle accurate” mode to the original 4.77Mhz clock speed, or it can be unlocked to run significantly faster. I used this mode a few years ago to create the world’s fastest PCjr! https://microcorelabs.wordpress.com/2017/01/02/worlds-fastest-pcjr/
Project under MCL86 in GitHub: https://github.com/MicroCoreLabs/Projects