Only “good” Pentium 4s have EM64T enabled

“ ONLY THE CYNICAL survive. Long after they are supposed to, probably. Intel has told everyone on the record now that it will soon switch all of its desktop processors over to support for 64-32 extensions – or iAMD64 as we dub it.

How will it do this? Well, the engineers at a fab will throw a switch and the number of the processors will change so that a 531 – a 3GHz Pentium 4 – will be exactly identical to a 530 except EM64T will be switched on.”