# Homework Help: Determining Number of Bits in MAR

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1. Feb 6, 2013

### SpiffWilkie

I'm trying to determine how many bits are required in the memory buffer register and in the memory address register given certain memory systems.

For example, given the below system, how many bits are needed in MAR, and MBR if the memory is word addressable and how many bits if the memory is byte-addressable.

64K x 32

From what I understand the bits in the MBR are equal to the number of bits in the memory unit, or 32 for this example. I'm having a hard time grasping the MAR concept, though.
If I'm using word address memory, would it just be 16 bits (26 x 210 = 64K)? I guess, I'm asking if the unit size is irrelevant in that case.
If the memory is byte-addressable, would it be 18 bits? 216 x 22 (since each unit is 4 bytes?)

Thanks for any insight.

2. Feb 7, 2013

### Staff: Mentor

All of your numbers look correct to me.

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