Macromodel option

I'd leave it alone. From Ken Kundert's book A Designer's Guide to SPICE and Spectre (hard to obtain now - it came out in 1995), Ken says in A.3.1.7 Macromodels:

Over the years Spectre has been tuned to run quickly on real circuits. These optimisations have the side effect of causing Spectre to run more slowly on circuits that deviate greatly from the norms of physical circuits. In particular, Spectre performs poorly with some macro-models. Setting this flag makes Spectre more tolerant of the aberrant behaviour exhibited by these macro models. With macromodels set, Spectre becomes more determined to efficiently pass through the abrupt discontinuities exhibited by some macromodels and uses local error criteria to allow huge voltage and currents at a subset of the nodes.

By default macromodels=no because otherwise Spectre runs more slowly on most circuits, but enabling it may cause Spectre to run much quicker on circuits that exhibit non-physical behavior.

The reasons why I suggest avoiding it are:

1. When this was added, it was quite commonplace to use a combination of ideal components, controlled sources, and even active devices with simplified models to try to fit and model circuit behaviour - so called "macromodels". In Spectre, nowadays, that is unusual - you would use behavioural models instead using Verilog-A for example which has more direct control and more appropriate ways of writing models.
2. There have been many, many years of optimisation of the simulator technology since then and I can't recall a case of where I've needed to use this; I rather doubt it's useful on modern circuits given other improvements in the simulation technology.

Andrew

thanks Andrew.