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Thread: When do I need the PAE Kernel?

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    Default When do I need the PAE Kernel?

    I have a 64 bit machine with 4 Gb RAM and presumably no need for the PAE Kernel.

    But I have a 32 bit machine also with 4GB RASM. Should I have the PAE kernel in that, or is it only needed for RAM > 4GB (or what, I'm hazy about the PAE Kernel).
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    Default Re: When do I need the PAE Kernel?

    Quote Originally Posted by swerdna
    I have a 64 bit machine with 4 Gb RAM and presumably no need for the PAE
    Kernel.

    But I have a 32 bit machine also with 4GB RASM. Should I have the PAE
    kernel in that, or is it only needed for RAM > 4GB (or what, I'm hazy
    about the PAE Kernel).
    Hi
    Some machines see it, some don't I would try the desktop, but during an
    install it should work out which one. You can always install both

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    Default Re: When do I need the PAE Kernel?

    I'm fairly certain kernel-desktop will see the RAM in most cases. But as M said, the installer will usually get it right.
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    Default Re: When do I need the PAE Kernel?

    Hi!
    PAE stands for physical address extension, you need it to address more than 4GB
    of physical RAM with a 32 bit processor, as mentioned above the installer should have already made this decision.

    When in YaST, be sure to click the details tab and verify the installer finds the amount of RAM installed, also a good idea to run the pre install memory test routine provided you have the time.

    On my hardware ( Athlon 64 x2 Qt-64 @ 2.1Ghz and 4 GB of Ram ) 1 full pass was about 2 hours and 3 min. it is a very thorough test, took a bit over 26 hours to run 13 passes.

    Regards, Cfn7
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    Default Re: When do I need the PAE Kernel?

    Quote Originally Posted by CFN7 View Post
    Hi!
    PAE stands for physical address extension, you need it to address more than 4GB
    of physical RAM with a 32 bit processor, as mentioned above the installer should have already made this decision.

    When in YaST, be sure to click the details tab and verify the installer finds the amount of RAM installed, also a good idea to run the pre install memory test routine provided you have the time.

    On my hardware ( Athlon 64 x2 Qt-64 @ 2.1Ghz and 4 GB of Ram ) 1 full pass was about 2 hours and 3 min. it is a very thorough test, took a bit over 26 hours to run 13 passes.

    Regards, Cfn7
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    True, but it does more than just extend the access to RAM. On a 32bit machine is simulates some 64bit functionality using only 32bit processing. Is it really needed if you don't have 4GB + memory unsure. My Laptop under 11.1 default install didn't use PAE first time and ran fine. After an unintentional mistake and re-install, the default used PAE and ran 2 to 5% faster with still only 2GB RAM.
    When your up to your a** in Alligators it's pretty hard to remember you intended to drain the swamp (author unknown)

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    Default Re: When do I need the PAE Kernel?

    Very informative, thank you all for that.

    I wonder if the opposition have any PAE-like code for 32 bit machines in their distros, or maybe in their latest, window 7, anyone know?
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    Default Re: When do I need the PAE Kernel?

    Quote Originally Posted by swerdna View Post
    Very informative, thank you all for that.

    I wonder if the opposition have any PAE-like code for 32 bit machines in their distros, or maybe in their latest, window 7, anyone know?
    Most distros do PAE

    Windows......'cough - cough' Don't make me laugh!
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    Default Re: When do I need the PAE Kernel?

    caf4926 wrote:
    > Windows......'cough - cough' Don't make me laugh!


    i ran a full 32 bit desktop for *years* (OS/2) before Redmond released
    their first consumer grade (aka: almost reasonably priced)..

    and, first ran 64 in 2005..

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    Default Re: When do I need the PAE Kernel?

    At the possible expense of taking your question more literally than you would like:

    Quote Originally Posted by swerdna View Post
    I have a 64 bit machine with 4 Gb RAM and presumably no need for the PAE Kernel..
    no, no need, but...


    Quote Originally Posted by swerdna View Post
    But I have a 32 bit machine also with 4GB RASM. Should I have the PAE kernel in that, or is it only needed for RAM > 4GB (or what, I'm hazy about the PAE Kernel).
    I'm not sure that there is ever a need for a PAE kernel, but, in some circumstances it may be desirable.

    On my laptop (1 G ram) and 11.1 I was surprised (and gratified) the installer automagically decided that the PAE kernel was appropriate and installed that for me without any intervention on my part. I was expecting to have to do that myself, so I was really, really happy to find that out (not that its a big issue, but it just gives you a 'warm 'n fuzzy' to have someone get it right without you having to intervene).

    PAE is commonly packaged with NX (no execute) and this gives an appreciable extra degree of protection against buffer overflow attacks. This, as much as anything was why I was keen on a PAE kernel.

    The non-PAE 32 bit kernel can only map 4G of memory, and, in practice, you get to see a bit less than that. But at, say, 2G or less, there is no need for PAE in order to see the full amount of memory, but NX may still be very desirable.

    Above 4G of memory, the PAE kernel can be used and can make available a memory space of 4G per process. For most people that could be an advantage, but you can come up with corner cases (one very big process and not much else) in which it doesn't really deliver much.

    For most recent x86-compatible processors, the technical possibility exists of running 64 bit software. Firstly don't think that this will cause it to run twice as quickly; it won't. Some things will run a bit more quickly, some will run a bit more slowly and the balance will probably be a slight, but not a big, advantage, except for special cases. Secondly, some memory structures are a bit bloated in 64 bit, so it is probably undesirable to run 64 bit on low memory systems, even if you have the option.

    HTH

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    Default Re: When do I need the PAE Kernel?

    The non-PAE 32 bit kernel can only map 4G of memory
    I thought it was nothing over 3GB
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