What's the mean access time in this task?

[kumar_eee]

cache access time 100 msec. main memory access time 800 msec, if the hit ratio is 95% , what is mean access time ...

 

[eecs4ever]

Re: Answer plz

mean access time = 95% * 100ms + 5%* 800ms = 95mS + 40mS = 135mS

 

[kumar_eee]

Re: Answer plz

Hi eecs4ever,
Thanks alot. For this type of problm's which book I have to read...

Added after 5 minutes:

Similar to the above prob...

cache access time is 100ns. main memory access time is 1000ns, hit ratio is .9, find mean access time?

Answer is: .9*100ns+.1*1000ns = 190ns....

Is it correct?...

 

[eecs4ever]

Answer plz

You are correct.

For this type of problem, you should read a probability book.

Discrete Mathematics and its Applications, by Kenneth H. Rosen, McGraw-Hill, Inc., New York
[5.3]

or

http://www.athenasc.com/probbook.html

chapter 1 is posted on the site. I think chapter 1 may be enough for similar problems , like the ones above.

Good luck.