ASP.NET IIS - when are requests queued?

The following article by Thomas Marquardt describes how IIS handles ASP.Net requests, the max/min CLR worker threads/Managed IO threads that can be configured to run, the various requests queues involved and their default sizes.

Now as per the article, the following occurs in IIS 6.0:

1. ASP.NET picks up the requests from a IIS IO Thread and posts "HSE_STATUS_PENDING" to IIS IO Thread
2. The requests is handed over to a CLR Worker thread
3. If the requests are of high latency and all the threads are occupied, then the requests are posted to the Application level request queue (this queue is per AppDomain)
4. Also ASP.NET checks the number of concurrently executing requests. The article states that "if the number of concurrently executing requests is too high" it queues the incoming requests to a ASP.NET global request queue (this is per Worker Process)

I want to know what is the "threshold value" at which point ASP.NET considers that the number of requests currently executing it too high and then starts queuing the requests to the global ASP.NET request queue?

I think this threshold will depend upon the configuration of max number of worker threads, but there might be some formula based on which ASP.NET will determine that the number of concurrently executing requests is too high and starts queuing the requests to the ASP.NET global request queue. What might this formula? or is this setting configurable?