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In a computer's central processing unit (CPU), the accumulator is a register in which intermediate arithmetic logic unit results are stored.. Without a register like an accumulator, it would be necessary to write the result of each calculation (addition, multiplication, shift, etc.) to cache or main memory, perhaps only to be read right back again for use in the next operation.
The hardware unit that performs the operation is known as a multiplier–accumulator (MAC unit); the operation itself is also often called a MAC or a MAD operation. The MAC operation modifies an accumulator a : a ← a + ( b × c ) {\displaystyle a\gets a+(b\times c)}
In 1967, Fairchild introduced the first ALU-like device implemented as an integrated circuit, the Fairchild 3800, consisting of an eight-bit arithmetic unit with accumulator. It only supported adds and subtracts but no logic functions. [7] Full integrated-circuit ALUs soon emerged, including four-bit ALUs such as the Am2901 and 74181.
A sample computer system, the Wombat 1, is provided with CPU Sim.It has the following registers: pc (program counter);acc (accumulator);ir (instruction register);mar (memory address register);
The MAR register is half of a minimal interface between a microprogram and computer storage; the other half is a MDR. In general, MAR is a parallel load register that contains the next memory address to be manipulated, for example the next address to be read or written.
A word to be stored must be transferred to the MBR, from where it goes to the specific memory location, and the arithmetic data to be processed in the ALU first goes to MBR and then to accumulator register, before being processed in the ALU. The MDR is a two-way register. [2]
Accumulator (computing), in a CPU, a processor register for storing intermediate results; Accumulator (computer vision), discrete cell structure to count votes, standard component of the Hough transform; Accumulator (cryptography), a value, determined by a set of values, that allows one to verify if any one of the original values is a member of ...
Where these two bits are equal, the product accumulator P is left unchanged. Where y i = 0 and y i−1 = 1, the multiplicand times 2 i is added to P; and where y i = 1 and y i−1 = 0, the multiplicand times 2 i is subtracted from P. The final value of P is the signed product.