> It also needed three supply voltages; +5v, +12v, and -5v. That made it tough to power it from a single-voltage power supply or battery.

According to https://www.allaboutcircuits.com/news/mc34063-the-switching-..., the solution - the MC34063 - isn't _exactly_ a design that's contemporary with the Altair or other 1970s micros, but was introduced in the early 1980s. That would put it closer in age to the Commodore 64 which, in spite of its much smaller size, still indeed does not fit in an Altoids tin.

Very cool project nonetheless!

https://sunrise-ev.com/z80.htm