[phenixbb] autobuild : use of ncs

i read and see that autobuild finds ncs automatically and uses it. i have one .pdb with one copy of the model for segid's A and B, and chainid's A and B. however, i notice sometimes in density modification that ncs has "NO" flags as to its use, and the output .pdb's have a single chain in them. refinement has sensible .eff's and such for ncs, there's find_ncs_* output, but some .log's suggest it is not specified or used. so just generally, how is ncs used - e.g. is it strict, which would explain a single chain the output .pdb? -bryan