AMD 2901 bit-slice processor family includes 2901 and 2903
4-bit microprocessors slices, 2909 and 2911 microprogram sequencers,
2910 microprogram controller and other support chips.
The 2901 processor consists of 16 4-bit registers, 4-bit ALU and associated
decoding/multiplexing circuits. The ALU accepts 9-bit microinstructions
that specify source operands,
ALU function and the destination register. The 2901 ALU can perform
8 different functions (they are encoded into 3 bits within the
microinstruction): addition, subtraction and logic operations.
Multiple 2901 bit-slice processors could be combined together
to build microprocessors with any data width (in 4 bits increments).
Enhanced version of 2901, AMD 2903 has 9 new special ALU functions used
for implementation of multiplication, division and normalization operations.
The number of arithmetic and logic ALU functions in 2903 was increased to 15.
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