from 4GB of mem to 8GB - Hardware

This is a discussion on from 4GB of mem to 8GB - Hardware ; On 2008-02-05, General Schvantzkopf wrote: > On Tue, 05 Feb 2008 10:42:38 -0500, alex wrote: > >> General Schvantzkopf wrote: >>> With 8G you will definitely want to switch to a 64 bit kernel. >> >> Can you explain? This ...

+ Reply to Thread
Page 2 of 2 FirstFirst 1 2
Results 21 to 22 of 22

Thread: from 4GB of mem to 8GB

  1. Re: Q: 32-bit systems and large RAM

    On 2008-02-05, General Schvantzkopf wrote:
    > On Tue, 05 Feb 2008 10:42:38 -0500, alex wrote:
    >
    >> General Schvantzkopf wrote:
    >>> With 8G you will definitely want to switch to a 64 bit kernel.

    >>
    >> Can you explain? This is not a trick question, I just thought that
    >> 32-bit systems can go to 64 gigs with PAE.
    >>
    >> In fact I will shortly be setting up a linux server with 4 dual-core
    >> CPUs and 32G of RAM for simulation and analysis. I use some third-party
    >> software for which 32-bit versions are very stable and well-tested, but
    >> 64-bit versions are new and can have warts, so I somewhat prefer a
    >> 32-bit setup.
    >>
    >> What traps I would be stepping into if I went with a 32-bit system?

    >
    > 32 bit systems can use 64G of RAM when you use PAE, however each thread
    > is limited to 4G.


    Actually, on Linux the default is 3G -- reserving 1G for the kernel. Also,
    PAE is rather slower than natively being able to address all that RAM. I
    would strongly suggest going 64bit on your new system.

    > You should be able to run the 32 bit version of your simulation software
    > on a 64 bit system, I do that with NCverilog because the 32 bit version
    > is faster.


    Exactly.

    --
    Joshua Baker-LePain
    Department of Biomedical Engineering
    Duke University

  2. Re: Q: 32-bit systems and large RAM

    On Tue, 5 Feb 2008 21:34:17 +0000 (UTC), Joshua Baker-LePain wrote:
    >On 2008-02-05, General Schvantzkopf wrote:
    >> On Tue, 05 Feb 2008 10:42:38 -0500, alex wrote:
    >>
    >>> General Schvantzkopf wrote:
    >>>> With 8G you will definitely want to switch to a 64 bit kernel.
    >>>
    >>> Can you explain? This is not a trick question, I just thought that
    >>> 32-bit systems can go to 64 gigs with PAE.
    >>>
    >>> In fact I will shortly be setting up a linux server with 4 dual-core
    >>> CPUs and 32G of RAM for simulation and analysis. I use some third-party
    >>> software for which 32-bit versions are very stable and well-tested, but
    >>> 64-bit versions are new and can have warts, so I somewhat prefer a
    >>> 32-bit setup.
    >>>
    >>> What traps I would be stepping into if I went with a 32-bit system?

    >>
    >> 32 bit systems can use 64G of RAM when you use PAE, however each thread
    >> is limited to 4G.


    >Actually, on Linux the default is 3G -- reserving 1G for the kernel. Also,
    >PAE is rather slower than natively being able to address all that RAM. I
    >would strongly suggest going 64bit on your new system.


    That is only true if a single process needs to address more than 3G.

    Otherwise, it is no slower. Processes have their 3G user address space mapped
    into the 64G physical address space with no slowdown whatsoever.

+ Reply to Thread
Page 2 of 2 FirstFirst 1 2