Without PHP_FCGI_x lines system got so much slow. I had to put them back. I noticed in the task bar there are always 1 or 2 php-cgi.exe processes while it must be 4. I splitted cgi.bat file into four individual files each handling one port. Now I have 4 php-cgi.exe processes and system is working even faster than before without any failures. Thanks! without you I couldn't figure it out.

Since I'm holding task manager open, I see that sometimes cgi processes get closed and that causes upstream errors again. Why they are getting closed? is there a closure timeout for inactivity?

Also since we're at it, how do I calculate my exact settings? number of cgi processes, max_requests, children? (i'm planning to go with php-fpm on ubuntu)

Say in my busy hour, I have 150 users online. each one sending a request per second. Should I calculate every page request with their images and scripts, adding one request for each?