1-bit computing


In computer architecture, 1-bit integers, memory addresses, or other data units are those that are wide. Also, 1-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size.
A serial computer processes data a single bit at a time. For example, the PDP-8/S was a 12-bit computer using a 1-bit ALU, processing the 12 bits serially.
An example of a 1-bit computer built from discrete logic SSI chips is the Wang 500 calculator as well as the Wang 1200 word processor series of Wang Laboratories.
An example of a 1-bit architecture that was marketed as a CPU is the Motorola MC14500B Industrial Control Unit, introduced in 1977 and manufactured at least up into the mid 1990s. One of the computers known to be based on this CPU was the WDR 1-bit computer. A typical sequence of instructions from a program for a 1-bit architecture might be:
This architecture was considered superior for programs making decisions rather than performing arithmetic computations, for ladder logic as well as for serial data processing.
There are also several design studies for 1-bit architectures in academia, and corresponding 1-bit logic can also be found in programming.
Other examples of 1-bit architectures are programmable logic controllers, programmed in instruction list.
Several early massively parallel computers used 1-bit architectures for the processors as well. Examples include the Goodyear MPP and the Connection Machine. By using a 1-bit architecture for the individual processors a very large array could be constructed with the chip technology available at the time. In this case the slow computation of a 1-bit processor was traded off against the large number of processors.
1-bit CPUs can now be considered obsolete; not many kinds have ever been produced, still as of 2020 many MC14500B chips are available from brokers for obsolete parts.