Accumulators are different from memory registers because location.

Accumulators are built inside the chip, RAM is built outside the chip. The exact architecture of the accumulators and the RAM may or may not be identical, but they are functionally the same.

So accumulators are registers. They are just the registers located within the chipset. They serve to hold intermediate results close at hand.

I read that accumulators are more expensive than RAM chips, but I don't know why. I have some ideas, but I'm not sure.


E.g. 3*(4+1) = 15 requires the addition to happen, and the intermediate result of that addition is then multiplied by 3.

If the processor had to send the 15 off to RAM, only to retrieve it a moment later, this would take much more time than if it stores the 15 inside the chip and then retrieves it a moment later. The time for the electrical signals to physically traverse the wires is what's different.


Usually, an accumulator is just a memory register. In this case, whenever data is sent to the register, that data overwrites whatever data was previously left in the register.

Sometimes, depending on the chip, an accumulator might be hardwired to an adder. In this case, whenever a number is sent to the accumulator, the accumulator adds the value, creating a running total. This set up requires a means of clearing the register, setting the value to 0, as needed.

Modern chips have hundreds of memory registers in them.

The CU directs the connections between the ALU and the accumulators, and the accumulators and the RAM.