A modern smartphone is smaller than ENIAC or UNIVAC, but it has a lot more digital switches. UNIVAC had a little over 5,000 vacuum tubes packed into its 25 m3 case. An iPhone 12 has 11.8 billion transistors packed into the phone’s 80 mL case, which is about a trillion times more computer per liter. If you built an iPhone with vacuum tubes instead of transistors, packed together with the same density as they were in UNIVAC, the phone would be about the size of five city blocks when resting on one edge.
