Pop quiz  11/9/2017

1. How many 256G memory cards do you have to buy to get 1T of memory?

2. You can buy 4-bit by 256 memory cards. That is, there are 8 bit addresses
2^8 = 256, and each addressable location contains 4 bits.
You are able to build memory using these units. 
How many memory cards do you need to buy to put together 16 bit word, 1K address space?

3. You are copying 1G of memory to back-up. The data transfer rate is 10^9 bytes/sec.
How long will it take?

4. You write a program that will execute in 2050 bytes total (code plus data).
Memory is available in 1K units.  How many memory cards are required?

5. Give 12.3 mW in scientific notation.

6. Give 0.0123 Gjoules in scientific notation.



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SOLUTIONS

1. 2^2  ( 4 cards)

2. 16  ( you need 4 rows of cards (256 * 4 = 2^10) and 
         4 columns of cards (4 * 4 = 17 bits) )
         
3. approx 1.074 sec
  ( 1G bytes / 10^9 bytes/sec) = 2^30 / 10^9 approx 1.074 * 10^9 / 10^9 )
  
4. 2050 bytes / 1024 bytes/card approx= 2.00195.
But can only have whole cards. So need
 ceiling (2050 / 1024) = 3 cards
 
5. 1.23 * 10^(-2)   ( 1.23E-2  )

6. 1.23 * 10^7      ( 1.23e7)