Text book: Computer Organization and Architecture, Fourth Edition Chapter 9 and

Question

Text book: Computer Organization and Architecture, Fourth Edition

Chapter 9 and Exercise 10

Questions:

Suppose that a RISC machine uses 5 register windows

(a) How deep can the procudure calls go before register must be saved in memory? ( This is what is the maximum number of active procedure calls that can be made before we need to save any registers in memory?)

(b) suppose two more calls are made after the maximum value from part (a) is reached. How many registered windows must be saved to memory as a result.

(c) Now suppose that the most recently called procedure returns. Explain what occurs.

(d) Now suppose one more procedure is called. How many register windows need to be stored in memory

Explanation / Answer

a) Since ,one window(set) of registers can be vissible by
one procedure execution environment at any time.
And N-Window register file can save only N-1 active procedures.
Thus depth of 4 prcedures calls are allowed in the
RISC with 5 register windows.

b) 1st and 2nd window registers need to be saved to memory

c) since, most recently saved window pointer is maintained,
when a procedure returns( means a register window becomes
free) ,the most resently saved register window is restored.

d) one register window

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