A 10,000 rpm (revolutions per minute) harddisk can transfer data at a rate of 16

ID: 3552257 • Letter: A

Question

A 10,000 rpm (revolutions per minute) harddisk can transfer data at a rate of 160 Mbps (megabits

per second). The time to find a track is negligible. Determine the data amount for which it takes

as long to transfer it off the disk as the time it takes to find the right sector.

- Step 1: Determine the time it takes for a half-rotation. Hint: compute the number of

revolutions per millisecond and work from there.

- Step 2: Translate the data transfer into kilobytes per millisecond.

- Step 3: Multiply the two numbers together to get the data amount.

given 10,000 rpm

1Mbps=1024 Kbps

1second = 1000 milliseconds

1 minute = 60 seconds

step 1:

10000 rotations -- 1 minute

10000 rotations -- 60 seconds

1rotaion -- 60/10000 seconds

1rotation --0.006 seconds

1/2rotation -- 0.003 seconds

--3 milliseconds

step2:

data rate of 160 Mbps

160Mbps = 160 *1024 Kbps

=160*1024 *10^3 Kbpms (Kilo bits per milliseconds)

step3:

the data amount.:

time taken for 1/2 rotation * datarate in Kbpms

= 3ms* 160*1024*10^3 Kbpms

=491520Kb of data is transfered.

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