Does setInterval make a website sluggish?

[sorenchr]

Hi, I'm currently considering implementing an Ajax script a lá:

 

http://yensdesign.com/2008/11/creating-ajax-websites-based-on-anchor-navigation/

And http://beski.wordpress.com/2009/04/21/ajax-pagination-with-anchor-navigation/

 

Both of the scripts use a setInterval function, set to every 300ms. I was wondering if this would make my website slow or anything in that manner (particularly slow/old computers) to a noticeable degree?

 

Thanks for your time