[averagewall]

Transistors in TTL logic use mA of input current because they're bipolar, not FET transistors.

[blattimwind]

In classic TTL the input currents are also very asymmetric, e.g. for a high level you mustn't draw more than a few dozen µA out of an input, for a low level you have to draw something like 1.5 mA or so.

This is different from current-steering based logic (all kinds of ECL, including CML/SCL) were the current in the circuit stays the same, but only takes a different path depending on state. Supply current is largely independent of circuit state with these.

[lisper]

That's true, but we're talking about computers here. Computer chips don't use TTL, they're all CMOS, which uses FETs (MOSFETs to be precise).

[kevin_thibedeau]

CMOS didn't exist when the first transistorized computers were made.

[lisper]

Ah, right. I thought the OP was referring to modern CPUs.