64 bits is neither here nor there in a vaccuum. you want 64 bits if
a) you need more than 4GB of memory, or
a) those extra registers and direct vlong really matter for
performance.
otherwise it's just a lot of extra zeros.
it's kind of silly to run 64-bit linux on a machine with <= 4GB of
memory.
Some testing we did about a year ago showed that (for us) even the
extra registers -- I always thought the sweetest-sounding part of the
deal -- help sometimes, but not always. I ended up thinking it was
because caches hadn't necessarily grown apace with address space. The
distance between cpu and main memory seemed to have expanded again...
64 bits was still the simplest path to > 4G memory for those linux
machines in that situation, but the observation surprised me.
--
Josh
