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  1. Hi All, Welcome to the J1 discussion area of the Gadget Factory Forum. The J1 is a compact, open source cpu, with a stack architecture optimised for executing the Forth language. It is ideally suited to fit into a variety of FPGAs, and James Bowman, the designer, has kindly made a build available that suits the Papilio hardware - specifically the Papilio Duo fitted with computing shield. Stack processors have been around quite a while - as described ion Philip J. Koopman's 1989 book "Stack Computers: The New Wave" The book introduces the concept of the stack computer and offers a detailed examination of 7 such examples both 16 bit and 32 bit. The book reviews stack computers that were being developed in the mid-1980s, at the same time as the ARM RISC architecture was in its infancy. In 1985, Charles H. Moore introduced the Novix NC4016 - a 16 bit stack computer based on a gate array. This device was revolutionary in it's day and faster than the nearest Intel x86 offering - despite the fact that it used only 1% of the transistors of the Intel part. It ran at 8MHz and showed how hardware and software could be optimised together for speed and efficiency. The J1 is a close descendent of the Novix, James Bowman has incorporated many of the ideas pioneered in the NC4016 and adapted them for efficient implememtation in FPGA hardware. The result is a 32bit Forth processor in a common Xilinx FPGA that runs at 180MHz. I would like to invite you to join a journey of discovery into the fascinating world of soft core processors, stack machines and the Forth language. Ken Boak co-Moderator London 13th September 2015