ByPass iView server EP 5.0 SP 5.0

Question:

Can anyone give me/point me to a detailed explanation of what byPassing the iView server does? The reason I ask is I have created a number of iViews that use eventing. When I run the iViews in the portal under isolation level 1 any of the iViews that are subscribed to the sender load the entire portal page over + the changes into its iframe. If I set it to level 4 bypass iView server, it works fine....Any one run into this? Why are the subscription iViews loading the entire portal page?

Thanks