UGC NET CSE | July 2018 | Part 2 | Question: 8

Question

A graphic display system has a frame buffer that is 640 pixels high , 480 pixels high and  1 bit of color depth. If the access time for each pixel on the average is 200 nanoseconds, then the refresh rate of this frame buffer is approximately:

• A. 16 frames per second
• B. 19 frames per second
• C. 21 frames per second
• D. 23 frames per second

Answer 1

Frame buffer size $= 640 * 480 = 307200$ pixels

Access time = $200$ nanoseconds$/$pixel $= 200*10^{-9}\space$ sec$/$pixel

No.of pixels accessed in $1\space sec$ $= \frac{1}{200 * 10^{-9}\space sec /pixel} = 5$ x$10^6$
  
Refresh rate $= \frac{access\space rate}{frame\space size}$ $= \frac{5 *10^6\space pixels/sec}{307200\space pixels}$
     $= 16.27 $ per sec.
 

So, the answer is $(1)$.

Answer 2

Width = 640 px

height = 480 px

color depth = 1 bit / px

Total screen pixel  = 640 X 480 = 307200

memory required for total pixel = w X h X color depth = 640 X 480 X 1 = 307200

Answer is option A

1 pixel takes 200 nanoseconds

whole screen will take = 307200 X 200 = 61440000 nanoseconds

In 1 nanosecond  1/61440000 screen

In 1 second (1 X 1000000000)/61440000 screen. ( 1 s = 1000000000 ns)

= 16.27604166

So, it comes closer to option A.

Answer 3

Here 640 pixel wide is width of screen means horizontal line on screen and 480 pixels height is means vertical line on screen.

Now                                 width (w) = 640 px             and                   height (h) = 480 px

                                        Total = 640 x 480 = 307200

                                        Color depth = 1-bit/px
                                        Memory required for total pixel = w x h x Color Depth
                                        Memory required for total pixel = 640 x 480 x 1-bit = 307200

                                       1 pixel takes 200 nano second to refresh
                                       To refresh the whole screen = 640 x 480 x 200 ns = 61440000 nano second
                                     
                                       For 1 nano second =   ____1____  screen
                                                                            61440000 
                                                                                                                                                        9
                                      Now Convert nano seconds to second we multiply above value with 10
                                                                                                     9
                                      For 1 nano second =   ____1____  x 10  = 16.2760 = 16 (Approximately)
                                                                            61440000

                                      The above solved values is closed to Option (1).

answer taken from http://www.studyviral.in/2018/07/ugc-net-july-2018-computer-science-and_79.html