- from Intel the model 4004
- from NEC the processor family µPD75X
- from Texas Instruments the TMS1000 series
- from Hewlett-Packard the HP-Saturn family
as well as various other designs.
In simplified terms, 4 bits means that the processors are designed in such a way that 4 bits can be processed simultaneously or during one cycle ( word length ). This includes the external and internal design of data and address buses , the execution of the register set and the processing units .
Processors with 4-bit architecture were made in the 1970s u. a. Used for pocket calculators because with this data size the numbers 0 to 15 could be implemented in binary coding and the numbers 0 to 9 in the BCD coding, which is favorable for display modules .
They were and are also used in many household appliances (e.g. washing machines ) and entertainment electronics ( televisions , video recorders ) for simple control and monitoring tasks. While 'classic' 4-bit processors such as the Intel 4004 are rarely used today, processors such as the 4-bit processor family µPD75X from NEC can still be found in many new household appliances. These microprocessors are usually equipped with many digital inputs and outputs, various timers and a real-time clock including interfaces for the direct control of LC displays .