Every communication uses different protocol layers of the ISO-OSI 7-layer model (e.g. transport layer). The protocol layers can be realized both through software on the communication processor and through software on the computer. If the computer is to do this task, then you have SoftNet card. If the work is done by the communication processor itself, then you speak of a HardNet card.
For the definition of whether you have a HardNet or SoftNet, therefore, it is important to know where the data exchange between the layers takes place. SoftNet communication processors simulate the required protocol via the computer and use the card only for the physical adapting of the signals to the bus system.
A HardNet card on the other hand has its own processor that handle the protocol processing independently. The driver software in the operating system (e.g. Windows NT) for this communications processor simply adds layers 6 and 7 to the protocol.
If you have to make a decision about which communications processor you want to use, then you must take the loading of the computer into account. If your computer is already heavily loaded by an application (e.g. WinCC), then it is always recommended to use a HardNet card.
System requirements, Minimum requirements, Performance