
The out.wrspice codes:

drhack
  See the va source, there is an expression for the Dr parameter that
  differs between 6.0 and 6.1, causing differences in model output.
  The out.wrspice-drhack have the 6.0 expression.

cv1
  The cvmod=1 parameter/value is given.  This seems to be needed for
  6.0 compatibility.

rds2
  The rdsmod=2 parameter/value is given.  This seems to be needed for
  6.0 compatibility.
