arandom question

[veins <veins_(_at_)_skreel_(_dot_)_org>]

Hi
I was having fun writting a small utility that displays pixels randomly in some
window and I noticed something.

When reading from /dev/urandom, pixels are displayed everywhere:
  http://www.skreel.org/~veins/pics/urandom_entropy.jpg

but when reading from /dev/arandom, i get the following:
  http://www.skreel.org/~veins/pics/arandom_entropy.jpg
showing that a particular value is never read from the device.

I left the app running and I noticed that very often, similar lines appear after
some time showing that the another value comes out very often compared to other
as the clearer lines show:
  http://www.skreel.org/~veins/pics/arandom_entropy2.jpg

I was just wondering if this is a normal behaviour or not from arandom ?

-- veins