The 4-bit computer 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.

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 architectures.

Applications

Most 4-bit microprocessors were used almost exclusively in calculators and toys.

4-bit microprocessor

• Intel 4004
• Intel 4040
• AMI 9209
• Hitachi HD35404
• National IMP-4
• Fairchild PPS-25
• Rockwell PPS-4
• Rockwell PPS-4/2
• Toshiba T3472
• TMS1000
• NEC μCOM 4
• HP Saturn (64-bit register, 4-bit data path)

4-bit microcontrollers

• MARC4
• TLCS-47
• NEC μPD75X
• NEC µPD612X
• NEC µPD172XX
• Epson S1C63

4-bit discrete chips

• AMD Am2901, a 4-bit slice RALU