This seems like a fine time to remind people that Ben Eater made an entire video series on building an 8-bit programmable computer from simple TTL chips (including detailed explanations of logic gates)
Best of all, it's #Meltdown and #Spectre proof
https://www.youtube.com/watch?v=HyznrdDSSGM&list=PLowKtXNTBypGqImE405J2565dvjafglHU