Explain the meaning of Tc, Cc, Tm and Cm in the following memory system specification.
Tc = 100 ns
Cc = 10^(-4) $/bit
Tm = 1200 ns
Cm = 10^(-4) $/bit
a. Calculate the cost of 1 MByte of main memory using the above parameters.
b. What is the cost of 1 MByte of cache memory?
c. If the effective access time is 10% greater than the cache access time, what would be the hit ratio (H)?
Tc = cache access time = 100 ns
Tm = main memory access time = 1200 ns
Cc = cost of cache memory = 10^(-4) $/bit
Cm = cost of main memory = 10^(-4) $/bit
a. Cost of 1 MByte of main memory (considering no cache memory)
= 1 MByte * 8 bits/Byte * Cm $/bit
= 2^20 * 8 * 10^(-4) $
The solution considers that in case of a cache miss, first the content is brought from main memory into the cache and then access proceeds as if there was a cache hit. It also gives the effective access time (EAT) expression if it is not the case.