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The 74S181 4-bit ALU bitslice resting on a page from the datasheet. The 74181 is a 4-bit slice arithmetic logic unit (ALU), implemented as a 7400 series TTL integrated circuit. Introduced by Texas Instruments in February 1970, [1] it was the first complete ALU on a single chip. [2]
To do this, the algorithm treats each integer as an ordered collection of ALU-size fragments, arranged from most-significant (MS) to least-significant (LS) or vice versa. For example, in the case of an 8-bit ALU, the 24-bit integer 0x123456 would be treated as a collection of three 8-bit fragments: 0x12 (MS), 0x34, and 0x56 (LS). Since the size ...
The Zilog Z80, although it is an 8-bit microprocessor, has a 4-bit ALU. [11] [12] Although the Data General Nova is a series of 16-bit minicomputers, the original Nova and the Nova 1200 internally processed numbers 4 bits at a time with a 4-bit ALU, [13] sometimes called "nybble-serial". [14]
For example, two 4-bit ALU chips could be arranged side by side, with control lines between them, to form an 8-bit ALU (result need not be power of two, e.g. three 1-bit units can make a 3-bit ALU, [2] thus 3-bit (or n-bit) CPU, while 3-bit, or any CPU with higher odd number of bits, hasn't been manufactured and sold in volume). Four 4-bit ALU ...
AMD Am2901: 4-bit-slice ALU. Am2900 is a family of integrated circuits (ICs) created in 1975 by Advanced Micro Devices (AMD). They were constructed with bipolar devices, in a bit-slice topology, and were designed to be used as modular components each representing a different aspect of a computer control unit (CCU).
The very fastest shifters are implemented as full crossbars, in a manner similar to the 4-bit shifter depicted above, only larger. These incur the least delay, with the output always a single gate delay behind the input to be shifted (after allowing the small time needed for the shift count decoder to settle; this penalty, however, is only incurred when the shift count changes).
At each advance, the bit on the far left (i.e. "data in") is shifted into the first flip-flop's output. The bit on the far right (i.e. "data out") is shifted out and lost. The data is stored after each flip-flop on the "Q" output, so there are four storage "slots" available in this arrangement, hence it is a 4-bit register.
A full adder can be viewed as a 3:2 lossy compressor: it sums three one-bit inputs and returns the result as a single two-bit number; that is, it maps 8 input values to 4 output values. (the term "compressor" instead of "counter" was introduced in [ 13 ] )Thus, for example, a binary input of 101 results in an output of 1 + 0 + 1 = 10 (decimal ...