An electronic pet flap is fitted with an RFID receiver to provide an automated security system that unlocks the pet flap as the animal approaches and locks it again once it has moved away. A unique collar worn by the pet is also fitted with an active RFID transponder. a) The active RFID transponder worn by the animal is powered by a small battery. Why might a passive system not be suitable in this instance? [1]

b) Describe the principles of operation of the RFID system in locking and unlocking the pet flap. [3]

c) Suggest a potential problem with this system.

When making changes to optimize part of a processor, it is often the case that speeding up one type of instruction comes at the cost of slowing down something else. for example, if we put in a complicated fast floating-point unit, that takes space, and something might have to be moved farther away from the middle to accommodate it, adding an extra cycle in delay to reach that unit. the basic amdahl's law equation does not take into account this trade-off. a. if the new fast floating-point unit speeds up floating-point operations by, on average, 2ă—, and floating-point operations take 20% of the original program's execution time, what is the overall speedup (ignoring the penalty to any other instructions)? b. now assume that speeding up the floating-point unit slowed down data cache accesses, resulting in a 1.5ă— slowdown (or 2/3 speedup). data cache accesses consume 10% of the execution time. what is the overall speedup now? c. after implementing the new floating-point operations, what percentage of execution time is spent on floating-point operations? what percentage is spent on data cache accesses?

Suppose a cpu with a write-through, write-allocate cache achieves a cpi of 2. what are the read and write bandwidths (measured by bytes per cycle) between ram and the cache? (assume each miss generates a request for one block.)

In simple terms, how would you define a protocol?