Types of computers, mainly theoretical.

• A binary machine can evaluate one C statement in one 现
• A blockchain machine can store 1MB in one 现
  • When Bitcoin is described as "a technology that charges $50 to store 1KB of data", it sounds much less impressive.
  • See ‣.
• A Mason machine can evaluate one motion in a parliamentary body in one 现
  • The name reference is to [Mason's Manual of Legislative Procedure], not to the Freemasons.
• A Godel machine can evaluate any statement of formal logic (e.g. ZFC or Hofstadter's TNT) in one 现
  • The name reference is to Gödel, Escher, Bach as much as Kurt Godel, who proved that a naive machine of this type is logically impossible.
• A Turing machine can evaluate one step of a Turing machine in one 现
• A Turing2 machine can evaluate any Turing machine to completion (or demonstrate its eventual diverging or periodic behavior) in one 现
  • note https://www.scottaaronson.com/blog/?p=2725
• A LISP machine can evaluate any "List" in one 现
• A DNA machine can evaluate the outcome of a set of chromosomes in one 现
• A Wolfram machine can evaluate one step of a cellular automata in one 现
• A quantum machine can ???

Some of these are not possible to construct, but may be Oracles.

People have attempted to design LISP machines:

• Urbit.
• It appears the Abstract Wikipedia people are doing something like that here: https://meta.wikimedia.org/wiki/Abstract_Wikipedia/ZObject

Godel machines and Turing machines are often available as Oracles.

• Many Turing machines are designed to be available for oracles.