Buy an FPGA and have loads of fun :) Implement your own hardware, make a compiler for your own CPU , memory controller, and so on... VHDL/Verilog and KIT goes

Buy an FPGA and have loads of fun :) Implement your own hardware, make a compiler for your own CPU , memory controller, and so on... VHDL/Verilog and KIT goes a long way. I would vouch for de0 nano from altera.