Chapter 5, Problem 5.10.4E

Explanation of Solution

Reuse time threshold for the year 1987:

To covert KIB to MIB, multiply the value of MIB into 0.000976563.

$\begin{array}{c}\text{Reuse time thresholds = }\frac{\left(\frac{\text{Disk cost}}{\text{DRAM cost in KIB}}\right)}{\text{Disk Access Rate}}\\ \text{=}\frac{\left(\frac{\text{15000}}{5000\times \text{0}\text{.000976563}}\right)}{15}\end{array}$

$\begin{array}{c}=\frac{\left(\frac{15000}{4.8828}\right)}{15}\\ =\frac{3072}{15}\\ =204.800\simeq 205\sec onds\text{.}\end{array}$

Reuse time threshold for 1987 is 533 seconds.

Reuse time threshold for the year 1997:

To covert KIB to MIB, multiply the value of MIB into 0.000976563.

$\begin{array}{c}\text{Reuse time thresholds = }\frac{\left(\frac{\text{Disk cost}}{\text{DRAM cost in KIB}}\right)}{\text{Disk Access Rate}}\\ \text{=}\frac{\left(\frac{\text{2000}}{15\times \left(\text{8}\times \text{0}\text{.000976563}\right)}\right)}{64}\end{array}$

$\begin{array}{c}=\frac{(\frac{2000}{15\times 7}}{}\end{array}$