Multiple CGI/FastCGI processes on IIS 8.5

i have a IIS 8.5 server with php 5.4.24. When request increase on my running site then huge CGI/FastCGI open and site become unreachable. site down and give 500 internal server ERROR. I have tried in many ways but problem remaining same. as per my observation only 2-3 process stay active . rest other process stay inactive and make the system slow.
Is their any body can help me to figure it out the solution.

necessary configuration parameter is as below:
in php.ini:

max_execution_time=30 max_input_time=60

IIS->FastCGI Settings:

MaxInstance=0 PHP_FCGI_MAX_REQUESTS=100000

I have already checked the following links . But don’t get any proper solution.
multiple-php-cgi-exe-processes-on-iis
FastCGI
Using Fast CGI

Please check the necessary images as below:

enter image description here


Source: stackoverflow-php