This system process handles displaying the error screens, such as "an error has occurred, the system needs shutdown". This can also display a register dump for exceptions, and info for fatal errors. (Normally the black-screen errors are displayed on retail, while the latter is displayed on development units.)
The register dump/fatal error info can also be written to nandrw/sys/native.log. On retail consoles, the system does not notify ErrDisp that any user-land exceptions occurred, ErrDisp is only notified for this on dev/debug units. Therefore, on retail consoles native.log only contains info from fatal errors. Starting with 5.0.0-11 ErrDisp no longer writes logs to native.log, except when the error-type is value 5 and when other checks with the errorinfo structure are successful (normally processes using this port never use error-type 5).
The bottom screen displays the error screen like "error has occurred", even with a development 3DS. The top screen can display the development error info, this is only displayed when ENVINFO bit0 is clear, for a development 3DS.
ErrDisp handles "returning" to Home Menu via NSS:RebootSystem, which triggers a hardware system reboot.
ErrDisp error port "err:f"