In the context of DRAM timing, what is a pseudomaximum. What DRAM parameter is a pseudomaximim? What are the implications of a pseudomaximum for design engineers?
What will be an ideal response?
The pseudomaximum is a rather unusual concept. The prefix pseudo means false and it is a false maximum in the sense in the sense that it is not really a maximum and can, in fact, be longer. A pseudomaximum is a value whose maximum value is the least large value possible. You can use larger values but that is not necessary. In
everyday life, the price we pay for things is a pseudomaximum; if a book costs $10 that is its lowest high price (you can pay more than $10 if you really want to, but it you do, you are throwing money away).
In a DRAM, the parameter tRCD (see below) which is the time between RAS* low and CAS* low has a minimum value and a pseudomaximum. The pseudomaximum is given by the time for the address hold following RAS* low, plus the time to multiplex the address from row to column plus the column address setup time before CAS* low.
The implication of a pseudomaximum is that you can exceed it, but if you do you are throwing away speed by waiting longer than is strictly necessary.
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Explain why this protocol prevents a global deadlock among transactions.
The kill-wait concurrency control of Exercise 20.32 is based on locking. When it is used in a distributed system, it is referred to as the wound-wait protocol. We assume that a distributed transaction uses RPC to communicate among cohorts so that when the two-phase commit protocol starts, all cohorts have completed. The kill primitive is replaced by a wound primitive. If the cohort of transaction, T1, at some site makes a request that conflicts with an operation of the cohort of an active transaction, T2, at that site, then if TS(T1) < TS(T2) then wound T2 else make T1 wait where wound T2 means that T2 is aborted (as in the kill-wait protocol), unless T2 has entered the two-phase commit protocol, in which case T1 waits until T2 completes the protocol. What will be an ideal response?
__________ allows a distributed system to grow without affecting the existing applications and users.
a) Transparency b) Scalability c) Reliability d) all of the above
The use of microfilm and microfiche provides all of the following advantages EXCEPT ____.
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A. document B. word C. line D. paragraph