how to improve Active Requests for application pool?

I'm confused by the result of a test.

I used a webstresstester to concurrently submit 2,000 http requests in very shot time, and i get above result using  "appcmd list requests". 

And I found the "Acitve Requests count" can not exceed 10 in my server (win7 + 4cpus), and it's the same when i test on another server(win7+2cpus).

I suspect the system somewhere limit the Active Request to 10, am i right?  Is it the same for a server with windows server 2008 and 16cpus?  if it's true, how to increase this limit to provide more process power?

Hope someone can help me out. Thanks for any help.

Regards,

James