Why is the 64bit JVM faster than the 32bit one?

Question

Recently I\'ve been doing some benchmarking of the write performance of my company\'s database product, and I\'ve found that simply switching to a 64bit JVM gives a consiste

Answer 1

Without knowing your hardware I'm just taking some wild stabs

• Your specific CPU may be using microcode to 'emulate' some x86 instructions -- most notably the x87 ISA
• x64 uses sse math instead of x87 math, I've noticed a %10-%20 speedup of some math-heavy C++ apps in this case. Math differences could be the real killer if you're using strictfp.
• Memory. 64 bits gives you much more address space. Maybe the GC is a little less agressive on 64 bits mode because you have extra RAM.
• Is your OS is in 64b mode and running a 32b jvm via some wrapper utility?