From OpenSCADAWiki
As an example, lets examine an industrial PLC "Siemens S7-315" during requesting him on the bus ProfiBus (1,5 Mbit/s). The average processing time of the MPI-request of this controller is 30 ms. If you use the synchronous mechanism for each signal, i.e. one request for each signal, then in one second we can get something about 33 signals. And if you apply the asynchronous mechanism, i.e. in the MPI-package to receive up to 220 bytes or 110 signals of integer type of 16-bit, then we can for one second get up to the 3630 signals. As you can see, the effectiveness of the asynchronous mechanism in this case is 110 times, that is the maximum capacity of MPI-package.