kpf - But there are strong indications that there is more required to port software to AMD-64 to take full advantage of its capabilities.
Nope, there is not. 1)Make code 64 bit clean 2)Verify that system library calls are correct 3) recompile
A compiler will take care of the extra registers so no effort is required there.
As i see applications gaining performance from being ported to AMD-64 and applications dropping in performance, both using the same compiler, it sure seems there is something to be done on the programming-level - just that I would not be able to tell what it is.
Nope. Recompiling the code in 64 bits should get you 0-15% slowdown. That is normal due to the larger variables. Extra registers on AMD64 give some of the lost performance back, sometimes more than what was lost when going to 64 bits. System libraries is the OS concern, and it seems like they can add a little to the slowdown. However, all this is well worth the extra address space!
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