Bit-serial architecture

In digital logic applications, bit-serial architectures send data one bit at a time, along a single wire, in contrast to bit-parallel word architectures, in which data values are sent all bits or a word at once along a group of wires.

All computers before 1951, and most of the early massive parallel processing machines used a bit-serial architecture—they were serial computers.

Bit-serial architectures were developed for digital signal processing in the 1960s through 1980s, including efficient structures for bit-serial multiplication and accumulation.[1]

Often N serial processors will take less FPGA area and have a higher total performance than a single N-bit parallel processor.

See also


  1. ^ Denyer, Peter B.; Renshaw, David (1985). VLSI signal processing: a bit-serial approach. VLSI systems series. Addison-Wesley. ISBN 978-0-201-13306-6.

External links

1-bit architecture

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 computer built from discrete logic SSI chips were the Wang 700 (1968/1970) and Wang 500 (1970/1971) calculator as well as the Wang 1200 (1971/1972) 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 (ICU), 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:

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 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 (PLCs), programmed in instruction list (IL).

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 (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.

1-bit CPUs can meanwhile be considered obsolete, not many kinds have been produced and none are known to be available in the major computer component stores (as of 2019, a few MC14500B chips are still available from brokers for obsolete parts.).

Autonetics Recomp II

The Autonetics RECOMP II was an early transistorized computer attached to a desk that housed the input/output devices. It was introduced by the Autonetics division of North American Aviation in 1958. Its desk integration made it a hands-on small system intended for the scientific and engineering computing market.

The computer weighed about 197 pounds (89 kg), 400 pounds (180 kg) including input-output.

Bit slicing

Bit slicing is a technique for constructing a processor from modules of processors of smaller bit width, for the purpose of increasing the word length; in theory to make an arbitrary n-bit CPU. Each of these component modules processes one bit field or "slice" of an operand. The grouped processing components would then have the capability to process the chosen full word-length of a particular software design.

Bit slicing more or less died out due to the advent of the microprocessor. Recently it's been used in ALUs for quantum computers, and has been used as a software technique (e.g. in x86 CPUs, for cryptography.)


The LGP-30, standing for Librascope General Purpose and then Librascope General Precision, was an early off-the-shelf computer. It was manufactured by the Librascope company of Glendale, California (a division of General Precision Inc.), and sold and serviced by the Royal Precision Electronic Computer Company, a joint venture with the Royal McBee division of the Royal Typewriter Company. The LGP-30 was first manufactured in 1956 with a retail price of $47,000—equivalent to about $433,000 in 2018.The LGP-30 was commonly referred to as a desk computer. It was 26 inches (660 mm) deep, 33 inches (840 mm) high, and 44 inches (1120 mm) long, exclusive of the typewriter shelf. The computer weighed approximately 800 pounds (360 kg) and was mounted on sturdy casters which facilitated movement of the computer.

Serial computer

A serial computer is a computer typified by bit-serial architecture — i.e., internally operating on one bit or digit for each clock cycle. Machines with serial main storage devices such as acoustic or magnetostrictive delay lines and rotating magnetic devices were usually serial computers.

Serial computers required much less hardware than their parallel computing counterpart, but were much slower.

Serial decimal

In computers, a serial decimal numeric representation is one in which ten bits are reserved for each digit, with a different bit turned on depending on which of the ten possible digits is intended. ENIAC and CALDIC used this representation.

Instruction set
Word size
Core count

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