[tasty_freeze]

The Z80 had that many transistors, not gates

The CMOS rule of thumb is one gate is 4 transistors (eg a 2-input NAND). But the first Z80 was nmos, and so the equivalent count is harder to state. 3 transistors per 2 input nmos gate is a rough first order guess, but in nmos wide gates still need only a single load resistor, and designers sometimes used dynamic logic to save even more transistors.

[vardump]

Ohh... This is embarrassing! I work in embedded/low level and I have always thought that gate == transistor. It's really obvious in retrospect...

I stand corrected.

[marshray]

It's not a crazy idea, there are indeed logic types that implement some gate types with a single transistor. For example, https://en.wikipedia.org/wiki/Resistor–transistor_logic

These were more commonly used back when transistors were expensive.