On 07/16/11 7:50 PM, david wrote: > If the I386 (or i686, never could figure out why the name change) I386 was the original 386 CPU, which ran at speeds from 16 to 33Mhz i486 includes a few additional instructions on the 486 processor, and IIRC, ran at speeds from 25 to 100Mhz i586 is the original pentium, at 60, 66, 90, 100 up to about 133Mhz i686 is the pentium pro and pentium-II, -III, -IV and everything newer. i686 added a few minor new instructions but also has additional memory management functionality missing from the earlier versions. its just gotten silly to try and keep backwards support for the early versions of the CPUs that have been obsolete for so long. really, we should have compiler targets for optimizing on the P4 'netburst' CPUs and another for the core processors as they are all pipelined differently. as it turns out, however, the core 2 and core I3/5/7 do pretty well with pentium-II and -III style optimization strategies, as well as, of course, the x86_64 support. -- john r pierce N 37, W 122 santa cruz ca mid-left coast