Java Programming

I am looking for information about how Java performs on Linux vs Windows and how the results are affected when a 64 bit jvm is used.
Disk access or IO are not important, I would really like to see some benchmarks on floating point arithmetic and/or heavy memory access, assuming that on all environments enough physical memory could be addressed so the extra available memory space for 64 bit os'es/jvm's is not important.

I have been searching on Google but didn't find any useful recent results, only some very old stuff.

Does anybody know how the OS and the JVM affect performance? I could imagine that Java VM's are a little less optimized on Linux because of the fact that Linux has a smaller marketshare, but maybe that is not true?

Also I could imagine that 64 bit JVMs could be faster because they could use more cpu registers, on the other hand they could slow down a little because all memory pointers are twice as long so more data should be processed?

Any comments are greatly appreciated!