Hi Peter, Yeah, the home built processor is great fun. I did a Xilinx VirtexII one when the parts first appeared and learnt a lot about the carry chain, those FMUX thingies, and the mighty 'mult_and'! It also teaches you a lot about the dual port block rams and multipliers. I called it nanoblaze, kind of halfway between Micro and Pico, because it used about 250 LUTs, 16 bits, 16 GP regs in a LUT RAM file, stack and program in a block ram, multiply instruction with the hard multiplier. If you target a particular architecture you can get suprisingly good performance, I got ~90MIPS in a VirtexII-slowestgrade, non-pipelined, i.e. 1 clock per most instructions including conditional relative jumps. Even single cycle interrupts! Once again, as you can tell(!!), I found it great fun, and an excellent way to learn about the fabric of the FPGA. Also, can teach you a lot about floorplanning and performance optimisation. I also used it to learn PERL to write the assembler, which was probably the best thing to come out of the whole project! BUT... I'd almost certainly NOT use it in a commercial product, too much documentation involved and soon every FPGA will have a hard processor anyway. Good luck, Syms.