The number of simultaneously connected machines for an Inventory task is driven by the configuration settings on the Automation Role server(s) that are deployed. In a single-server implementation the built-in Automation Role server is limited to 16 threads per task -- which typically translates to about a dozen simultaneous connections. The number of threads in the pool is user configurable -- on Automation Server Settings tab of Eminentware Servers node -- so you can decrease or increase this to manage the number of simultaneous connections.
In addition, you can also throttle the task by bandwidth utilization. Launch the EminentWare Server Wizard from the EminentWare Servers node, and the second screen allows you to engage bandwidth throttling for all connections to/from the selected Patch Manager server.