Building the computer from scratch isn't insanely hard. Writing the OS and TCP stack is, though. (I have done some of bth as part of degree at CMU, but not at

Building the computer from scratch isn't insanely hard. Writing the OS and TCP stack is, though. (I have done some of bth as part of degree at CMU, but not at the same time. Had to write a multitasking OS, no networking, and then separately design and build a machine from not-quite discrete components - we used 290x bit-slices and PALs.)