Problems with the speed of the function GetCommModemStatus

I have a compiled application in eVC++3 that runs perfectly in one IPAQ 3700 (PPC 2002). It uses CreateFile and GetCommModemStatus to count the cuantity of times the RLSD (Receive Line Signal Detect) goes through o to 1.

If I run the same binary in one IPAQ h2210 appear the problems. The same happens if the application is recompiled with eVC++4

The problem is that GetCommoModemStatus in the h2210 is extremely slow. When the RLSD moves between 0 and 1 many times for a second, GetComModemStatus delays more than 100 ms!!, On the other hand if the line is quiet GetComModemStatus is immediately. This, in the IPAQ 3700 with Pocket Pc 2002 does not happen.

I have tested with and without ActiveSync and with BlueThoth dissabled.

Any idea?

Thanks.