What's the difference between Classic and Super Server?

http://www.firebirdfaq.org/faq25/

Does Firebird support SMP?

http://www.firebirdfaq.org/faq2/

Why is the connection to the server so slow?

http://www.firebirdfaq.org/faq52/

2. If you have CPU that supports hyperthreading try disabling it to see if that helps. If you can multi-core CPU (dual core, quad core), set the CPUAffinity setting in firebird.conf