Speed question

Hi, I’ve a question: I’m working with SDL and sprites. I see a very
interesting thing, if I work with a very big sprites or with a lot of
sprites I see that the speed is always the same and all the sprite moves
very slowly in the screen. If I use 1 pixel as movement step the sprite is
slow but if I use a step of 3 or 5 pixels the sprite will “jump” from a
position to another one.
It seem that there is a sync signal that slow down the sprite. Have you got
any ideas to resolve this problem?
Sorry for my very poor english.
Thanks a lot. Bye.