[SMARTY] Controling buffer: php/smarty or apache?

Hi,

I am facing a strange problem.  My site, even tough designed to appear
quickly at user's browser, appears at "once".  If I test the static HTML
version it starts to appear as downloaded If I test the php generated
version the page seems render as a whole.

I am using smarty as a template and it seems to be related to a buffer
somewhere: php/smarty or apache.

I've used microtime and from the begin of the php script until after the
smarty->display it takes from 0.05s (min) to 0.32s (max)

Any tips of how can I figure out what is "slowing" down my site?

tks