x64 operating systems
ETS5 is a native x64 application. The advantage x64 applications is that they can address more RAM than x86 applications.
ETS3 & ETS4 device plug-ins
ETS3 & ETS4 device plug-ins are only available as x86 software and can therefore be the reason to put ETS5 in x86 compatibility mode.
Compatibility Mode app
ETS5 can be put in x86 compatibility mode by means of the 'Compatibility Mode' app. This app is upon ETS5 installation installed and licensed, but needs to be activated explicitly. Although Apps are not available when ETS runs in Demo mode, Compatibility Mode may also run when ETS runs in Demo mode.
It is recommended to only activate this app when really necessary, because activating it means that ETS will work as x86 software instead of x64.
Apps can be actived/deactived via the 'Apps' list at the right side of the ETS status bar.