1) Which of the following memories are possible? Which are reasonable? Circle al

Question

1)      Which of the following memories are possible? Which are reasonable? Circle all that apply? Please explain your answers.

(P = possible, R = reasonable)

a) 9-bit address, 512 cells

b) 10-bit address, 2048cells

c) 10-bit address, 1024cells

d) 8- bit address, 512 cells

Hint * Two Explanations from two differeent professors, im not sure who is right:

Professor A: The "trick" to these problems is recognizing that an n-bit memory address allows 2^n cells. It is not "possible" to address more cells than this and it's not "reasonable" to waste address bits and address fewer cells. The cell size has no relationship to the number of bits in the address.

Professor B:

To be possible, we need to make sure that we can address all the cells. I.e. given a n-bit address, we can uniquely identify upto 2 n cells. To be reasonable, we want to make sure that we are making good use of the address space, and that the overall size of the memory is sensible.

Explanation / Answer

An n-bit memory address allows 2^n cells. It is not "possible" to address more cells than this and it's not "reasonable" to waste address bits and address fewer cells. The cell size has no relationship to the number of bits in the address.      

a) 9-bit address, 512 cells.

This is reasonable. An 9-bit memory address allows 2^9 cells=512 cells.

b) 10-bit address, 2048cells

This is not reasonable. An 10-bit memory address allows 2^10 cells=1024 cells.It requires 12-bit memory addess.

c)10-bit address, 1024cells

This is reasonable. An 10-bit memory address allows 2^10 cells=1024 cells.

d)8- bit address, 512 cells

This is not reasonable. An 8-bit memory address allows 2^8 cells=256 cells only. But we have 512 cells. so,it requires 9-bit memoery address.

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