1) get poky sources (1.5 +) NOTE: The poky source should not have an already-made 'build' directory within 2) in a fresh shell session, source oe-init-build-env-memres 3) in conf/local.conf modify BB_NUMBER_THREADS and PARALLEL_MAKE to be different than 1 4) in conf/local.conf, change MACHINE to qemux86-64 5) issue 'bitbake core-image-minimal' -notice bitbake is using only 1 thread -notice image built is for qemux86 I believe that local.conf is not interpreted.
This sounds like a cache validation bug, the file is used but it doesn't reload the file when it has changed.
#5535 treats the same issue *** This bug has been marked as a duplicate of bug 5535 ***