So it seems, noone's arguing to keep the current default and it is clearly not appropriate. Ok, we just have to choose a better default then. Here's what I suggest: 1. Change the default to i686. 2. Add a notice to the release notes for the release that contains this change. The notice will state what changed and how the default can be changed (by adding instruction-set=xxx to bjam command line). 3. Drop support for 80386, so i486 is the minimum for the whole Boost, unless a specific library has its own requirements. This is already de facto true at least for Boost.Atomic and Boost.SmartPtr, as well as those libraries which uses them or boost::detail::atomic_count. I'm not insisting on #3, although it seems to be a logical conclusion of the discussion. If noone objects I can do the change and provide the text for release notes. PS: Sorry if I'm rushing things. I just want this change to make it into 1.54, and this will make life a little easier for Boost.Log, which I also want to push for this release.