Part I Create a set of three priority interrupts and show how they are executed

Question

Part I Create a set of three priority interrupts and show how they are executed between times 0 and 80 ns. Assume: Only one program or interrupt can run at a time Each interrupt takes 20 ns to complete The priority of the interrupts ranges from IRQ6 as the highest priority interrupt to IRQ0 as the lowest priority Each level of priority interrupt need not be included. Show your results as in the following format using as many times as needed: Time Action 0 ns: Start of Main Program

Part II Explain the relationship among disk platters, tracks, sectors, and clusters.

Explanation / Answer

PART A

Draw a Time line from 0 to 80ns, with tick marks at every 10 ns.

Then show when each Interrupt occurs, on the time line, remembering that when a higher priority event occurs, the lower priority even is suspended, and only finishes when it is the highest priority remaining event.

You will find that the sequence is

0 - 10 Main
10 - 20 IRQ1 (10 ns of execution remains)
20 - 35 IRQ3 ( 5 ns of execution remains)
35 - 50 IRQ4 ( 5 ns of execution remains)
50 - 70 IRQ6 (completes)
70 - 75 IRQ4 (completes)
75 - 80 IRQ3 (completes)

PART B

Disks are made physically of one or more platters coated with magnetic media. Most desktop/laptop disks now only use one platter.
Each platter has a head on it, one on each side usually. A fine stepper motor (or magnetic driver) moves the heads a step at a time, to each track. A track is like a magnetic ring on the platter. Each ring is made up of "sectors", each usually 512 bytes long (or 1024, etc...) The number of sectors varies per ring, as the inside tracks (close to center) are smaller, thus less sectors fit on them.

Cluster is an operating system thing, it is more efficient to write/read data from a disk in chunks of sectors, like 2 or 4 or 8 sectors at a time, since they all pass under the head on the same revolution. A cluster can include sectors from two heads, on the same track at the same time (on opposite sides). Clustering can vary a lot.... Even Windows clusters data in 4096 byte chunks (or larger for large FAT32 partitions and so on...)

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