At Wed, 13 Jul 2011 09:17:55 +0100 (BST) CentOS mailing list <centos at centos.org> wrote: > > On Wed, 13 Jul 2011, John R Pierce wrote: > > > for many things, 32bit code is more compact and runs faster than 64bit > > code (primarily because the code is smaller, so it requires fewer > > fetches, more code fits in the cache, etc). 64 bit OS's totally > > compatible with 32bit applications. of course, if a process needs more > > than a couple gigabytes of address space, then 64bit is a no-brainer, > > but there's really not that many applications which need that sort of > > memory. > > Is that generally true? I thought running in 64bit got you access to twice as > many registers and that generally you'd expect better performance from x86_64 > code not worse. While pointers would be doubled in size, most of your memory > consumption would boil down to base types that'd be of the same size. For some applications the performance advantage of having more registers is small and the overhead of a larger executable is larger. There is not any sort of absolute or fixed rule that says that all applications *always* run faster, etc. when compiled for 64-bit, although most do. Also there are odd-ball applications that it is not worth the effort to make them 64-bit clean. And there are *still* a few bits and pieces that have not (officially) migrated to 64-bit (Adobe's Flash is not *officially* available as a 64-bit plugin, although a 'beta' 64-bit version is available). > > jh > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos > > -- Robert Heller -- 978-544-6933 / heller at deepsoft.com Deepwoods Software -- http://www.deepsoft.com/ () ascii ribbon campaign -- against html e-mail /\ www.asciiribbon.org -- against proprietary attachments