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  Opteron aka Athlon64
Experiences Posted by Beat Rubischon on Thursday August 26, @11:07AM
from the 64-bits-and-some-buts dept.
This morning, 05:35, I got an SMS. Not the one from my dancing partner I expected but from our BigBrother. Three of our new Athlon64 who scans for viiri and spam went down. We deployed 5 of them during the last two weeks and like to share our experience with you. Read on if you like to buy or operate an Opteron or Athlon64 based system.

Compared to Intel, which developed a complete new CPU called Itanium, AMD decided to enhance the existing i386 instruction set. An Athlon64 or Opteron based system - we call them from now on x86_64 - is compatible to any operating system which is running on IBM compatible PCs. So you may run DOS, any kind of Windows, Linux/i386 and others. There is no need to buy a non-x86_64 when you need a new computer. There is also no need to install a dedicated 64 bit operating system.

But, first of all, way should you use 64 bits? As short FAQ:

  • Are 64 bits faster then 32 bits?
    No. A CPU instruction is a CPU instruction and needs one ore more cycles in the CPU.
  • Are 64 bits cooler then 32 bits?
    No. The CPU is heating and needs also a fan.
  • Are 64 bits more stable then 32 bits?
    No. Read on to see why.
So, you will ask now "why should I use a 64 bits CPU?". There is one reason: Memory. In a 32 bit system, you may use up to 4GBtyes of memory in your program. Even on a high end, multiprocessor Xeon system with 64 GBytes of RAM, your single program may just use 4 GBytes of it. It's simple limited by the register size of 2^32 bytes which are 4294967296 bytes or 4 GBytes. People like our astronomers, who creates virtual galaxys, would like more then this in their simulations.

So let's install a true 64 bit operating system. Linux is available since a long time, but the distributions are still far away from beeing perfect:

Debian, our favorite distribution, has no true 64 bit support in Sarge and Sid. The stable i386 version works well. You will need Knoppix and debootstrap to install Woody - the current install medias would not boot.

Gentoo has a working 64 bit version for x86_64. Because of the large administration overhead, we cant use it.

Fedora has a working x86_64 port and is the only free available distribution which also supports 32 bits binarys on the fly. Like in Solaris, HP-UX, AIX or Irix, you'll find a /lib and /lib64, /usr/lib and /usr/lib64. We are using Fedora on our virus scanners to get all performance out of the CPU for Spamassassin, amavisd-new and ClamAV but also support uvscan which is a closed source 32 bit binary.

AMD invested a lot of money and manpower in the development of gcc, the GNU C Compiler. Modern gcc compilers produce highly optimized code for x86_64 which performs much better then i386 code on the same platform. A non-representative-benchmark (openssl speed rsa512) shows, that a recent Athlon is twice as fast as a PIV, 32 bits code on a Athlon64 is twice as fast as on the Athlon and 64 bits code on a Athlon64 is twice as fast as 32 bits code on a Athlon64. (don't trust any statistics you did'nt forge yourself :-)

On the other hand, the mixed mode of 32 and 64 bits is not as stable as it could be. Fedora's current Kernel 2.6.8-1.521 has a large memory leak when executing 32 bits code and was responsible for the SMS this morning.

Windows is available as a public Beta. We installed this system on one of our boxes for testing. It seems to work, but near every piece of hardware is still missing some drivers. Even more, there are currently two versions of Windows XP 64 Bit: One for Athlon64 and one for Itanium. Microsoft does not yet point at this difference, so be sure to get the right version! Applications are no problem - it seems to be possible to run near every application written for Win32.

Intel is also incorporating AMDs 64 bit instruction set in their Pentium IV and Xeon systems. Intel call this Extended Memory 64 Technology EM64T. It would be nice to view the benchmarks between AMD and Intel CPUs.

Our conclusion: Athlon64 is a fine CPU. Dont hesitate to buy and use one. But to use the whole power of the 64 bits, you shuld have a lot of knowledge or some time to wait.

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  • The Fine Print: The following comments are owned by whoever posted them.
    ( Reply )

    Re: Opteron aka Athlon64
    by dummkopf on Thursday August 26, @07:48PM
    so... why did you not do what george sigut did? he got RHEL 3 which so far seems very stable on 257 machines...

    cheers, h.

    [ Reply to this ]
    • Re: Opteron aka Athlon64
      by Beat Rubischon on Friday August 27, @08:19AM
      Operating a beowulf and a mailserver are quite different tasks. While hreidar must be running and a good partner like RedHat could help, our mailsacanners are a place where we collect some experiences running Linux/x86_64. This difference is the reason why we choose Fedora. We don't need professional support - in case of problems, we could switch back to our standard Debian installation. From the technical side Red Hat Enterprise is still running a 2.4 kernel and I don't think that someone runs 32 bit code on it. The performance boost from gcc3 on x86_64 is it worth to recompile programs ;-)

      [ Reply to this ]
      • Re: Opteron aka Athlon64
        by dummkopf on Friday August 27, @05:24PM
        make sense, but from my experience fedora is a piece of crap...

        have a good weekend, h.

        [ Reply to this ]
    Re: Opteron aka Athlon64
    by Axel Thimm on Monday September 20, @11:40AM
    Hi,

    > On the other hand, the mixed mode of 32 and 64 bits is not as stable as it could be.
    > Fedora's current Kernel 2.6.8-1.521 has a large memory leak when executing 32 bits code and was responsible for the SMS this morning.

    I have been hit by this for some time now and returned to the previous 2.6.7 based kernels.

    What workaround are you using? Is this a known bug to RH (bugzilla?). Any patch to apply? <:)

    Thanks!
    [ Reply to this ]
    • Re: Opteron aka Athlon64
      by Axel Thimm on Monday September 20, @12:21PM
      I have filed this with Red Hat under

      https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=132947

      [ Reply to this ]
    Re: Opteron aka Athlon64
    by Martin Ebnöther on Tuesday October 05, @11:29AM
    # Are 64 bits faster then 32 bits? No. A CPU instruction is a CPU instruction and needs one ore more cycles in the CPU.

    Wrong! All wrong! The correct answer would be:

    "Sure man! You'll be dead sexy with one of these! (Think 'Groupies')"

    Coolness isn't about temperature!
    [ Reply to this ]
    • Re: Opteron aka Athlon64
      by Beat Rubischon on Wednesday October 06, @08:26AM
      Well, the 64 Bits are not responsible for that impact. It's much more the cool box around it :-)

      Badly, no one sees that nice computer in the dark serverroom...

      [ Reply to this ]
    Kernelleak fixed
    by Beat Rubischon on Tuesday November 23, @08:21AM
    See Bug 132947.
    [ Reply to this ]
    The Fine Print: The following comments are owned by whoever posted them.
    ( Reply )

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