Today I learned that the CPU inside the TI-84 is from the 70s. The Zilog Z80 chip that powers the mathematics woes of high school and college students around the world used to be at the height of personal and business computing, now it plots my graphs and evaluates my integrals. I'm actually amazed that such an old chip has stayed in production for this long, and is probably more common than ever before. I wonder why TI didn't go for a more modern chip such as the ATmega 328p, SAMD21 M0, or one of their own chips when they designed the 84 and other calculators.