This multistage process is still how pretty much everything boots, BTW, except you start with a ROM rather than a human flipping switches. Back in those days a boot ROM was an expensive option you could do without.
The DG Nova hadware was simple largely because it was built in TTL and the ALU was a 74181. In the mid-1960's the final project in the logic design course was to design a DG Nova machine using TTL.
There's an archive with some pictures from an eBay listing here: https://entrex480.blogspot.com/2017/05/entrex-480.html?m=1
I need to read Soul of a New Machine again.