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Ubuntu 12.10: 32-bit vs. 64-bit Linux Performance

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  • #46
    i blame either memory alignment or pointer arithmetic(if its not the same) for those couple slower tests
    (compiler can too, but idk that)

    64bit program with proper memory alignment should take twice as much memory then the 32bit counterpart (also with memory alignment)
    what is not optimal for all things (space-time trade off)

    64bit cpu should be faster in all ways (except memory consumption, but memory speed should be the same and 64bit can fetch 64bits at a time, 32bit can 32) when working in 64bit mode as you at least have extra registers to play with (not faster by much as the cpu has "register renaming" and some extra tricks in bout modes)
    Last edited by gens; 10-18-2012, 09:44 AM.

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    • #47
      Originally posted by jakubo View Post
      whats the big deal with these pointers? is smaller pointers are good for performance, why not reduce them even further? would probably be an interesting thing when someday 128 bit may be introduced, to have a dynamic pointer size. if thats possible at all..
      there have been 64bit cpu's even 20 years ago, but have not been used for practical reasons
      mind you can use the 128bit sse registers for storing data and processing floating points in bout 32 and 64bit modes (in 64bit mode you get extra sse registers, same applies as above stated)


      http://www.cs.umd.edu/class/sum2003/...p/pointer.html
      about pointer arithmetic

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      • #48
        Originally posted by jakubo View Post
        would probably be an interesting thing when someday 128 bit may be introduced, to have a dynamic pointer size.
        AMD64 arch can theoretically handles up to 4 millions GB of RAM.
        So... it's too early to think about an Athlon 128.

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