The 4-bit architecture is a microprocessor 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 8-bit wide addresses.

Industry

Most of the first microprocessors during the early 1970s had 4-bit word length. Both the Intel4004 and the 4040 were 4-bits. The world's first single-chip microprocessor by Texas Instruments, the TMS1000, was also a 4-bit CPU. 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 architecture architectures.

Applications

Most 4-bit microprocessors were used almost exclusively in calculators and toys. 4 bits was a logical choice for many calculators that used BDC numbers representation.

4-bit microprocessor

• AMI 9209
• Fairchild 9405
• Fairchild PPS-25
• Hitachi HD35404
• HP Saturn (64-bit register, 4-bit data path)
• Intel 4004
• Intel 4040
• ITT 7151
• National IMP-4
• Rockwell PPS-4/1
• Rockwell PPS-4/2
• TMS1000
• Toshiba T3472
• WD CR1872

4-bit microcontrollers

• AMI S2000
• Epson S1C63
• Fujitsu MB8840/1
• Hitachi HD404729S
• Hitachi HMCS40
• National COPS I
• National COPS II
• National MM5799
• National MM57140
• National MM57152
• NEC μCOM-4
• Matsushita MN1400
• Matsushita MN1500
• MARC4
• OKI MSM6411
• Sanyo LM6402G
• Sanyo LC587004
• Sanyo LC587008
• Sanyo LC58E68
• Sharp SM552
• Toshiba TLCS-47

4-bit discrete chips

• AMD Am2900, a family of 4-bit bit slice chips