other commands like "Place Instance" and "Library Manager" do not
track cells in the internal database, and so are unable to place
a cell instance that does not have a corresponding file on disk
(e.g., a cell read from GDS or LEF).
Instead of a 6-character suffix generated randomly, the 6-character
suffix is generated by a hash algorithm from the device parameters.
If the cell parameters are changed, then the cell itself changes.
If the instance name was default (derived from the cell name) then
the instance name changes accordingly. The result is that there
cannot be two (auto-)generated cells with the same parameters but
with different cell names.
Tim Edwards