Back in the 80s I wrote an assembler and a simulator for a custom DSP before the board was manufactured (it was the 80s so several chips were required), and our team wrote and tested code for it before the board was ready. When the board was ready, we wound up having to modify the assembler and simulator because some control signals were wired backwards and it was easier to just change the instruction coding than to redo the layout. The tools ran on a Vax. Worse, it was Eunice, a Unix-on-top-of-VMS atrocity that we were stuck with because of code that needed VMS and other code that wanted a Unix-like system.