Seriously, 32-bit binaries still work fine under AMD64, so a recompile is not a pressing issue. Yet, that is not so under IA64 where the speed of the 32-bit code is not good at all.
I agree.
But a lot of people fail to realize that this is a two edged
sword. ISVs that want to sell their wares for use on IPF
boxes clearly have to recompile. OTOH, the growth in native
AMD64 software will be very slow IMO because ISVs will be
sorely tempted to skip the time and expense of creating and
supporting a separate distribution for AMD64 because the
standard 32 bit x86 version runs so well on Opteron.
Look how long it took for P4 optimized apps to become widely
available despite the fact that 1) ISVs knew that P4 would
rapidly become the dominant selling microarchitecture, 2)
the speedup on a P4 from optimizing the code was often very
substantial, much more so than recompiling for K8, and 3) P4
optimized apps ran just fine on older CPUs, in many cases
noticeably faster than previous releases. I think anyone
expecting a flood, or even a steady stream of AMD64 apps
next year is going to very disappointed.