Comment by GeorgeRichard

The rather good YouTube channel "Our Own Devices" has a couple of interesting episodes about these:

https://www.youtube.com/watch?v=iNhjfk9BTNA&pp=ygUcb3VyIG93b...

https://www.youtube.com/watch?v=pWA-M590bhY&pp=ygUcb3VyIG93b...