The 4-bit architecture is a microprocessor or computer architecture that has a datapath width or a highest operand width of 4 bits or a nibble. These architectures typically have a matching register file with registers width of 4 bits and 4-8-bit wide addresses.

Industry

Most of the first microprocessors during the early 1970s had 4-bit word sizes. Both the Intel 4004, the first commercial microprocessor, and the 4040 had a 4-bit word length, but had 8-bit instructions. Some of the first microcontrollers such as the TMS1000 made by Texas Instruments and NEC's μPD751 also had 4-bit words. 4-bit word were proven to be very limiting and by 1974 there was a shift to larger architectures such as 8- and 12- bit architectures.

In the microcontroller domain, the story is a little different. 4-bit microcontrollers found their way into many battery-powered and low power instruments and devices. Some 4-bit chips such as the Atmel MARC4 continued to be manufactured until very recently (2010s), those devices aimed directly at wireless devices such as RFID-related applications. Other 4-bit MCUs are still made to date such as the Epson's S1C60 and S1C63 MCU families. Modern 4-bit microprocessors, however, are much different to the first generation microprocessors of the 1970s - in terms of architecture, performance, and overall capabilities.

Applications

Most of the early 4-bit microprocessors were used almost exclusively in calculators and toys, later on for various utilities, video games, controllers, and early computers. 4 bits was a logical choice for many calculators that used BDC numbers representation.

Today, 4-bit chips such as S1C60 family are still manufactured are used in many low-power devices, wireless tools, and internet of things. Until recently Atmel's MARC4 was also a large player in the low-power RF/IR wireless market.

4-bit microprocessors

• AMD Am2900
• AMI 9209
• Fairchild 4700
• Fairchild 9400
• Fairchild PPS-25
• Hitachi HD35404
• HP Saturn (64-bit register, 4-bit data path)
• Intel 4004
• Intel 4040
• Motorola 10800
• National IMP-4
• Rockwell PPS-4
• TI TMS1000

4-bit microcontrollers

• Atmel MARC4
• AMI S2000
• Epson S1C60
• Epson S1C63
• Fujitsu MB8840
• Fujitsu MB8850/500
• Hitachi HD404720
• Hitachi HMCS40
• Hitachi HMCS400
• ITT 7150
• National MAPS
• National COPS I
• National COPS II
• NEC 17K
• NEC μCOM-4
• NEC μPD751
• NEC μPD707
• Matsushita MN1400
• Matsushita MN1500
• Mitsubishi MELPS 4
• MMI 5700
• OKI OLMS-40
• OKI OLMS-50
• OKI OLMS-60
• OKI OLMS-64
• OKI OLMS-65
• Rockwell PPS-4/1
• Sanyo LM6402G
• Sanyo LC587004
• Sanyo LC587008
• Sanyo LC58E68
• Sharp SM4
• Sharp SM5
• Sharp SMS
• Toshiba T3400
• Toshiba TLCS-47
• WD CR1872
• WD WD4200