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Multiple processors systems memory

1. What happens if two CPUs in a multiprocessor attempt to access exactly the same word of memory at exactly the same instant?
2. Why is there a limit on cable length in an Ethernet network?
3. In the discussion of how URLs are processed by a browser, it was stated that connections are made to port 80. Why?
4. When multiple processes need access to data, in what way is object-based access better than shared-memory?
5. When a browser fetches a Web page, it first makes a TCP connection to get the text the page (in the HTML language). Then it closes the connection and examines the page. If there are figures or icons, then it makes a separate TCP connection to fetch each one. Suggest two alternative designs to improve performance here

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1. What happens if two CPUs in a multiprocessor attempt to access exactly the same word of memory at exactly the same instant?

If the memory word in question was already loaded into the caches of the both the CPUs and both the CPUs wanted to access the same memory word, then it can be accessed from the two caches simultaneously.
If the word not present in the caches, then the memory bank containing that word can handle one access at a time. The hardware will have a mechanism to select one access to proceed, with the other having to wait. In fact, in most of the multiprocessor systems this arbitration happens only when the two CPUs both try to access the memory bus at the same time.

2. Why is there a limit on cable length in an Ethernet network?

Ethernet is a local area technology, with network operating within a single building which connects the devices in close proximity. At most, Ethernet devices could have only few ...

Solution Summary

Multiple processor system memory is analyzed. The solution provides a discussion of how URLs are processed by a browser.

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