Periodically_call_remote and server strain

Has anyone used periodically_call_remote to update something like a
chat? We want to poll the server every 5-8 seconds for updates. I am
expecting 100 people or less on the server at a given time all running
pages with periodically_call_remote. Is this going to pose too much
strain? (Running Fedora, MySQL, Apache, mongrel, etc. on the same box)
The server will also be processing the normal web app functions in
addition to this.