An earlier logic chip used as a building block for CPUs. Bit slice processors used arithmetic logic units (ALUs) that typically came in 4-bit increments, although 1- and 2-bit devices were also made. Connected to a control unit, the ALU slices were strung together to make larger processors (8-bit, 16-bit, etc.). They included inputs and outputs for borrow and carry bits (addition and subtraction require carrying to and borrowing from the digit on the left).|
In the early days of microprocessors, bit slice processors enabled larger CPUs to be built from off-the-shelf components, and products were made by AMD, Intel and National Semiconductor in the mid-1970s. Most notable was AMD's 2900 family of integrated circuits used in CPUs from Digital and others, which included the Am2901 4-bit slice ALU. See ALU.