There's a lot of CPUs around in VHDL or Verilog, e.g. * http://opensource.zylin.com/zpu.htm http://opensource.zylin.com/zpu.htm * http://www.altera.com/device

There's a lot of CPUs around in VHDL or Verilog, e.g. * http://opensource.zylin.com/zpu.htm http://opensource.zylin.com/zpu.htm * http://www.altera.com/devices/processor/nios2/ni2-index.html http://www.altera.com/devices/processor/nios2/ni2-index.html You could use ghdl , http://ghdl.free.fr/ http://ghdl.free.fr/, and supporting tools for simulation. Most FPGA vendors have a free version of their tools as well.