Cycle rates of Arduino Mega target in External Mode

I am working to convert C-code written in the Arduino coding environment to the Simulink/Embedded Coder environment. For stability, my control system needs to operate with a cycle rate of at least 100Hz. I am confident that this cycle rate can be achieved when operating on the Arduino Mega target. However, when in external mode (which is fantastic for troubleshooting) I see that the scopes/displays are only being updated at 5Hz. Is this the maximum cycle rate when connected in external mode, or is this simply the maximum data transfer rate between the target hardware and Simulink?

To put the question another way, is it possible to study control algorithms meant to be operated at 100Hz when in external mode?