Linear speedup of NONMEM on quad-core CPUs?

A few years ago there was a post about benchmarking results for NONMEM on a dual-core CPU ( http://huxley.phor.com/nonmem/nm/99nov212005.html ). Given the relatively recent release of Xeon quad-core processors I wanted to know if anybody has compared NONMEM runs on a machine with two dual-core processors to NONMEM runs on a quad-core CPU, or even NONMEM runs on a computer with two quad-core CPUs. Has anyone confirmed that having four or eight cores provides linear speedup of running four or eight NONMEM jobs? Alternatively, if anyone has confirmed that the speedup is not linear, what is the approximate speedup, and what was model number of the CPU(s)? If a similar topic has been discussed recently (in January or February) on this mailing list, could someone please re-post the information? I just joined in March 2007, and the archives seem to contain no messages from 2007. Thanks, Steve