Performance of 64-bit vs. 32-bit Windows Dual Core

mikemuch writes "ExtremeTech's Loyd Case has done extensive testing on the same dual-core Athlon X2 4800+ system to explore performance differences between Windows XP Professional x64 and good ole Win32. The biggest hurdle is getting the right drivers. There are a few performance surprises, particularly in 3D games."

Comments

After reading the benchmarks...

[vandy1]

I can only conclude that they made no attempt to use the extra registers. Of *course* an f'ing 32-bit system will outpace a 64-bit system; Why do you think most Solaris apps are still 32-bit?

The reason why x86-64 is a win is because there are more registers as well. This allows compilers to do a better job.

Standard phallacy

[vlad_petric]

The main performance gain from going to x86-64 does not come from larger operands and larger addressing space. It comes from a cleaned-up instruction set architecture and, most importantly, from a larger set of registers. x86-64 has 16 general-purpose registers whereas x86-32 arguably has about 7 GPRs. For x86-32, a compiler generally allocates 2 or at most 3 registers to variables. For x86-64, it can utilize ~12. This greatly reduces the number of loads and stores to the stack. The performance gain comes from the fact that it's much faster to communicate via a register than through memory.

BTW, I don't know about windoze, but in the Linux world going from 32 bits to 64 bits almost always seems to produce a performance gain of 10->20%. I personally tried a simulator I'm using with 64 bits (recompiled with gcc), and got a speedup of 12%.