Question

Consider a 64-bit computer with a simplified memory hierarchy. This hierarchy contains a single cache and an unbounded backing memory. The cache has the following characteristics:
• Direct-Mapped, Write-through, Write allocate.
• Cache blocks are 4 words each.
• The cache has 256 sets.

(a) Calculate the cache’s size in bytes.

(b) Consider the following code fragment in the C programming language to be run on the described computer. Assume that: program instructions are not stored in cache, arrays are cache-aligned (the beginning of the array aligns with the beginning of a cache line), ints are 32 bits, and all other variables are stored only in registers.

int N = 32768;
int A[N];
for (int i = 0; i < N; i += 2) {
A[i] = A[i+1];
}

Determine the following:
(i) The number of cache misses.
(ii) The cache miss rate.
(iii) The type of cache misses which occur.

(c) Consider the following code fragment in the C programming language to be run on the described computer. Assume that: program instructions are not stored in cache, arrays are cache-aligned (the beginning of the array aligns with the beginning of a cache line), ints are 32 bits, and all other variables are stored only in registers.

int N = 32768;
int A[N];
int B[N];
for (int i = 0; i < N; ++i) {
  B[i] = A[i];
}

Determine the following:
(i) The number of cache misses.
(ii) The cache miss rate.
(iii) The type of cache misses which occur.

Answer 1

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