When there are devices or instances in the layout that do not exist in the schematic, the Calibreview in Virtuoso will contain these items with "noxref" in their names. Warnings will be issued as the Calibreview is generated citing that the "noxref" items are not found in the schematic.
The "noxref" devices in the calibreview will not have any device properties copied onto them from the schematic (since they don’t exist in the schematic).
For the "noxref" devices being put into the Calibreview, any properties for these devices that exist in the CDF library but are not extracted properties (i.e. properties that are not found in the netlist from Calibre xRC) will be set to their default values from the CDF library.
The "noxref" devices in the Calibreview will then get any extracted properties (i.e. those in the Calibre xRC parasitic extraction netlist).
These applications of device properties to the calibreview happen in the order cited above in order to have the layout properties take precedence over all other device properties.
This is performed in this manner to insure simulation of the layout derived values for devices in the design, in order to produce a result that accurately reflects the layout.