computer science - Amdahl's law -- how does the book get $8000/131.58% = $38.00? -


did simple amdahl's law equation , received same answer(s) book...

fraction of work: 60% cpu, 40% disk. scpu = 1/((1-f)+(f/k)) = 1/((1-0.60)+(0.60/1.4)) = 120.69% sdisk= 1/((1-f)+(f/k)) = 1/((1-0.40)+(0.40/2.5)) = 131.58%

...with exception of following answer.

$8000/131.58% = $38.00 disk upgrade

how did book answer?? 8000/131.58 not 38. original question posted below.

original question

suppose daytime processing load consists of 60% cpu activity , 40% disk activity. customers complaining system slow. after doing research, have learned can upgrade disks $8,000 make them 2.5 times fast currently. have learned can upgrade cpu make 1.4 fast $5,000.

which choose yield best performance improvement least amount of money?

http://ubt.albabsd.org/semestri3/shk3/im/im-ch7.pdf

in book used 5000$ cost both cases. 5000/131.58 = 37.9996. mistake.


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