The combined controller overhead and seek time (i.e., the time required to move
ID: 3813721 • Letter: T
Question
The combined controller overhead and seek time (i.e., the time required to move the read/write head to the appropriate track) on a certain disk system is 14 milli-seconds on average. It also takes an average of one half revolution of the disk to get to the beginning of a requested sector. The disk rotates at a rate of 7200 revolutions per minute. Each track contains 128 sectors and each sector contains 512 bytes of data. Assume that the disk transfers data with no delay as fast as the data is read and that there are no gaps between sectors.
a) Excluding the data transfer time from the disk into the system memory, what would be the average time in milli-seconds required for the disk controller to complete a read operation for a single sector?
b) Excluding the data transfer time from the disk into the system memory, what would be the average time in milli-seconds required for the disk controller to complete a read operation that obtains all of the data from 4 consecutive sectors?
Explanation / Answer
> A=[3 four 1;
> two three 4];
>
> B=[ one two 3;
> four five 6;
> seven eight 9];
>
> [nRow1,nCol1]=size(A);
> [nRow2,nCol2]=size(B);
>
> if nCol1 ~= nRow2
> error('inner dimensions should match');
> end
>
> C = zeros(nRow1,nCol2);
>
> for i = 1:nRow1
> for j = 1:nCol2
> for k = 1:nCol1
> C(i,j) = C(i,j) + A(i,k)*B(k,j);
> end
> end
> end
>
> C
> -------------------------
>
> this offers
>
> C =
>
> twenty six thirty four forty two
> forty two fifty one sixty
>
> To verify
>
> A*B
>
> ans =
>
> twenty six thirty four forty two
> forty two fifty one sixty
>
> --Nasser
excellent.
Subject: manual formula for matrix operation [3X2]*[2X3]
From: Matt J
Date: twenty nine Sep, 2012 19:54:08
Message: four of four
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"Matt" wrote in message <k452ge$pso$1@newscl01ah.mathworks.com>...
> Having hassle turning out with a code that multiplies 2 matrices along. i can not simply use matlab to directly multiply then, I even have to come back up with a loop. i'm undecided a way to implement a loop however doing one thing like this sum(X(1,:).*Y(:,1)') gets the primary component within the increased matrix correct.