Accelerate your Drupal/Pressflow site using Varnish
The primary reason for switching to Pressflow is to use an HTTP accelerator such as Varnish
Apache Configuration
Adjust your Apache configuration to server the Drupal site on port 8080. Edit your Apache conf file and add:
Listen 8080
NameVirtualHost *:8080
Restart Apache and make sure you can access your site on that port.
Varnish Configuration