1-bit architecture

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Not to be confused with bit or One instruction set computer.
"1-bit" redirects here. For the oversampling digital-to-analog converter technology, see 1-bit DAC.
1 4 8 12 16 18 24 26 31 32 36 48 60 64 128 256 512
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Floating point precision
×½ ×1 ×2 ×4 ×8
Floating point decimal precision
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1-bit microprocessor MC14500BCP

A 1-bit computer architecture is an instruction set architecture for a processor that has datapath widths and data register widths of 1 bit (1/8 octet) wide.

An example of a 1-bit architecture that was actually marketed as a CPU is the Motorola MC14500B Industrial Control Unit.[1] 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.

Several early Massively parallel computers used 1-bit architectures for the processors. Examples include the Goodyear MPP and the Connection Machine. By using a 1-bit architecture for the individual processors a very large array (e.g.: the Connection Machine had 65,536 processors) 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.

A typical sequence of instructions from a program for a 1-bit architecture might be:

  • load digital input 1 into a 1-bit register;
  • OR the value in the 1-bit register with input 2, leaving the result in the register;
  • write the value in the 1-bit register to output 1.

This architecture was considered superior when the program makes the decisions rather than performing computations, ladder logic, also for serial data processing.[2]

1-bit CPUs can be considered obsolete now, not many kinds have been produced (MC14500B and WDR-1 known) and none known to be available in the major computer component stores (as of 2016, a few on eBay[3]). Finnish company Partco still sells MC14500B as spare part in 2017.[4]

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