@Harald Pretl, @Steven Bos I have created a sample

test_multisim.sch

schematic (that is placed in the

top.sch

schematic page) showing how to include different commands depending on selected simulator. This schematic simulates unchanged in

ngspice

and

Xyce

. Conditionals allows you to generate netlist code depending on any condition (for example the content of a tcl variable or an environment variable or return value of a procedure as in this case). No changes in xschem were done, i have only added a convenience procedure

sim_is_ngspice

that is now paired with already existing

sim_is_xyce

. This is the only reason you should update xschem if you want to test this example.

Wow @Stefan Schippers! This works super, see a quick comparison between ngspice serial (22.3s) and xyce serial (3.3s). This time I added the .spiceinit file which improved ngspice simulation speed but it is still a (large) difference that increases with larger circuits. I will make and share a 1-bit DAC to 10-bit DAC simulator comparison at some point.