The L1 cache of a 32-bit computer is direct-mapped, has 1024 blocks each holding

Question

The L1 cache of a 32-bit computer is direct-mapped, has 1024 blocks each holding 16 bytes, and includes a dirty bit. Answer the following questions assuming that all important data paths in the computer are 32 bits wide.

a. How many bytes of information from main memory can be stored in this cache?

b. How many bits of information are stored in the cache to help locate information within this cache?

c. How many bits of information are stored in the cache to determine if stored information is valid?

d. How many bits are stored in the cache to allow lazy enforcement of Rule 1 of the Memory hierarchy?

e. What is the ratio of the number of other “overhead bits” that are necessary for cache function to the number of “content” bits in this cache? [You may use a calculator to compute the required ratio to 5 significant digits.]

Explanation / Answer

a. How many bytes of information from main memory can be stored in this cache?

Answer:-

256 bytes.

b. How many bits of information are stored in the cache to help locate information within this cache?

Answer :-

tag size = 12 bits (16 bit address - 4 bit index)
(12 tag bits + 1 valid bit + 8 data bits) x 16 blocks = 21 bits x 16 = 336 bits

d. How many bits are stored in the cache to allow lazy enforcement of Rule 1 of the Memory hierarchy?

Answer:-

(12 + 1 + 8) X 16 = 336 bits .

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