Robert Heller wrote:
> At Wed, 13 Jul 2011 09:17:55 +0100 (BST) CentOS mailing list
> <centos@xxxxxxxxxx> 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.
mark
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