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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)}
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);
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.
An example of this approach is the MOS 6502, which had only a single register, in which case it is referred to as the accumulator, and a special "zero page" addressing mode that treated the first 256 bytes of memory as if they were registers. Placing code and data in the zero page meant the instruction was only two bytes long instead of three ...
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.
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 ...
add the contents of a memory cell to the accumulator. 3: TAC: Test accumulator contents performs a sign test on the contents of the accumulator; if minus, jump to a specified memory cell. 4: SFT: Shift shifts the accumulator x places left, then y places right, where x is the upper address digit and y is the lower. 5: OUT: Output