A processor can support a maximum memory of $$4$$ $$GB,$$ where the memory is word-addressable (a word consists of two bytes). The size of the address bus of the processor is at least ___________ bits.

Consider a machine with a byte addressable main memory of $${2^{20}}$$ bytes, block size of $$16$$ bytes and a direct mapped cache having $${2^{12}}$$ cache lines. Let the addresses of two consecutive bytes in main memory be $${\left( {E201F} \right)_{16}}$$ and $${\left( {E2020} \right)_{16}}$$. What are the tag and cache line address (in $$hex$$) for main memory address $${\left( {E201F} \right)_{16}}$$?

Assume that for a certain processor, a read request takes $$50$$ nanoseconds on a cache miss and $$5$$ nanoseconds on a cache hit. Suppose while running a program, it was observed that $$80\% $$ of the processor's read requests result in a cache hit. The average read access time in nanoseconds is __________.

An access sequence of cache block addresses is of length $$N$$ and contains $$n$$ unique block address. The number of unique block addresses between two consecutive accesses to the same block address is bounded above by $$k.$$ What is the miss ratio if the access sequence is passed through a cache of associativity $$A\, \ge \,k$$ exercising least-recently-used replacement policy?