3. (20p)A computer has a cache, main memory, and a disk used for virtual memory. If a referenced word is in the cache, 1 ns are required to access it. If it is in main memory but not in the cache, 10 ns are needed to load it into the cache, and then the reference is started again. If the word is not in main memory, 100 ns are required to fetch the word from disk, followed by 10 ns to copy it to the cache, and then the reference is started again. The cache hit ratio is 0.9 and the main memory hit ratio is 0.8. What is the average time in nanoseconds required to access a referenced word on this system?

(Practice) Although the total number of bytes varies from computer to computer, memory sizes of millions and billions of bytes are common. In computer language, the letter M representsthe number 1,048,576, which is 2 raised to the 20th power, and G represents 1,073,741,824, which is 2 raised to the 30th power. Therefore, a memory size of 4 MB is really 4 times 1,048,576 (4,194,304 bytes), and a memory size of 2 GB is really 2 times 1,073,741,824 (2,147,483,648 bytes). Using this information, calculate the actual number of bytes in the following: a. A memory containing 512 MB b. A memory consisting of 512 MB words, where each word consists of 2 bytes c. A memory consisting of 512 MB words, where each word consists of 4 bytes d. A thumb drive that specifies 2 GB e. A disk that specifies 4 GB f. A disk that specifies 8 GB

(Practice) a. Using Figure 2.14 and assuming the variable name rate is assigned to the byte at memory address 159, determine the addresses corresponding to each variable declared in the following statements. Also, fill in the correct number of bytes with the initialization data included in the declaration statements. (Use letters for the characters, not the computer codes that would actually be stored.) floatrate; charch1=M,ch2=E,ch3=L,ch4=T; doubletaxes; intnum,count=0; b. Repeat Exercise 9a, but substitute the actual byte patterns that a computer using the ASCII code would use to store characters in the variables ch1, ch2, ch3, and ch4. (Hint: Use Appendix B.)

If a microprocessor has a cycle time of 0.5 nanoseconds, what’s the processor clock rate? If the fetch cycle is 40% of the processor cycle time, what memory access speed is required to implement load operations with zero wait states and load operations with two wait states?