CasheHW - TLB miss NOTE: units are all ns EXCEPT disk...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
Problem 1: a) Possible: 4ns(TLB access) + 10ns(cache access) b) Possible: 4ns(TLB access) + 32ns( page table reference) + 10ns(cache access) c) Possible: 4ns(TLB access) + 32ns( page table reference) + 10ns(cache access) + 32ns(main memory reference) d) Not Possible: the cache value would be stale if the page no longer resides in page table) e) Possible: 4ns(TLB access) + 32ns( page table reference) + 256ms (disk reference) + 4ns(TLB access restart) + 10ns(cache hit) EFFECTIVE ACCESS TIME = .88(4ns + .95(10ns) + .05(32ns)) + .12(4ns +.998(32ns +.95(10ns) + .05(10ns + 32ns)) + .002(32ns + 256ms + 4ns + 12ns)) --------- ---------- ---------------------------- ------------------------------- cache hit cache miss cache hit or miss page table miss ------------------------------------------- ----------------------------------------------------- TLB hit Page Table hit ----------------------------------------------------------------------------------------------------------------
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: TLB miss NOTE: units are all ns EXCEPT disk access is ms. Problem 2: a. Write through should be used to maintain consistency. If some processors have a value cached, and one processor changes that value, the other processors would not know about that value. With a write through cache (in addition to a broadcast "invalidate" message) the processors would not be using stale values. b. As mentioned in the answer for part a, the problem is stale data. One way to solve this problem is to invalidate stale entries . A way to prevent the situation would be to require processors to specify whether the values were for writing or reading. Shared reading would be ok; however, when a processor wanted to write, it would have to either wait until the readers were done, or send an invalidate message to those readers. Exclusive access by writers would then be allowed....
View Full Document

Ask a homework question - tutors are online