What is the smallest processor on the socket (in size)?

Question

Iron

A rather trivial question, to which, with a cursory googling, I did not find an unequivocal answer. Additionally, can someone tell me a small processor, quite common (including in a non-working state) with inexpensive motherboards (again, non-working ones are of interest).

Answer 1

As others have written, clarification is required. What processor architecture, what is required of it, etc.
For example, there is an ATTiny13 in a DIP8 package, which fits perfectly into a DIP8 socket, about a centimeter in size.
Microcontrollers are also processors.
Raspberry Pi Zero generally costs 5 bucks and can replace a personal computer. But this is if we consider the entire board as a "removable processor"

Answer 2

Since neither the architecture nor the socket specified anything, then AVR.

Answer 3

As an example of a small processor, and it is a processor, not a microcontroller, I will cite Parallax P8X32A as an example. Available in dip package.