Robert Heller wrote:
At Wed, 13 Jul 2011 09:17:55 +0100 (BST) CentOS mailing list centos@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.
<snip> Coming in late, here, but 64 bit should run as fast or faster, since the registers are larger, and 64-bit hardware is optimized for by 64-bit compilers. In addition, you get twice as much data per fetch. The upshot is that there is no good reason for it to run slower.
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