Scan engine vs. module

[Gary@B]

I recently received a 9023 RT controller and 9114 chassis.  I have 7 modules installed, 9205, 9265, 9425, 9477, 9481, 9485, and 9264.  How do the installed modules affect CPU usage in scan mode.  Is a module scanned by virtue of being installed or do you need to access some I/O on a given module before it is added to the scan.  Does it take as long to scan every channel on a module as to scan one?   In my short experiments I have all seven modules in scan mode.  When I had DI0 and DI1 from the 9425 monitored using I/O Alias the scan engine used about 20% of the CPU.  When I added AI0 to the monitoring the scan usage went up to 50%.  When I added AI1 the scan usage didn't seem to change.

[Gary@B]

I played with this a little more.  I am monitoring the IO Alias using a desktop PC.  The amount of CPU usage on the cRIO varies with the loop rate of the monitoring VI on the PC.  So perhaps some of the problem is the network load on the cRIO as it is the server in this case.