$1.$ Figure $5-3($b$)$ shows one way of having memory$-$mapped $1/0$ even in the presence of separate buses for memory and I$/$O devices, namely, to first try the memory bus and if that fails try the $1/$O bus. A clever computer science student has thought of an improvement on this idea: try both in parallel, to speed up the process of accessing I$/$O devices. What do you think of this idea?$2.$One mode that some DMA controllers use is to have the device controller send the word to the DMA controller, which then issues a second bus request to write to mem$-$ory. How can this mode be used to perform memory to memory copy? Discuss any advantage or disadvantage of using this method instead of using the CPU to perform memory to memory copy.Chapter $61.$ Students working at individual PCs in a computer laboratory send their files to be printed by a server that spools the files on its hard disk. Under what conditions may a deadlock occur if the disk space for the print spool is limited$?$ How may the deadlock be avoided?$2,$ City streets are vulnerable to a circular blocking condition called gridlock, in which intersections are blocked by cars that then block cars behind them that then block the cars that are trying to enter the previous intersection, etc. All intersections around a city block are filled with vehicles that block the oncoming traffic in a circular manner. Gridlock is a resource deadlock and a problem in competition synchronization. New York City's prevention algorithm, called "don't block the box," prohibits cars from entering an intersection unless the space following the intersection is also available, Which prevention algorithm is this? Can you provide any other prevention algorithms for gridlock?