Whoever wrote these models seems to have tried their best to emulate r2_cmc in ngspice. Like @User noted, they were kind enough to leave the P and Q parameters intact in high_po. Some more curiosities: • Defined width high_po resistors seem to be a custom fit and not based on r2_cmc. • xhigh_po, high_po and their fixed width counterparts have a factor for Pelgrom's law • xhigh_po__base also uses some custom fitting. • xhigh_po is a complete implementation of r2_cmc, including E field calculation.