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Thread: 64-bit kernel panics if memory remap enabled in BIOS

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  1. #1
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    Question 64-bit kernel panics if memory remap enabled in BIOS

    I have total 6 GB of RAM installed.

    Ubuntu 12.04 64-bit flavours refuse to install with a kernel panic indicating hardware failure if I enable memory remap in BIOS (which led me to change the memory module, luckily I happened to have a spare one lying around). If I disable the memory map in BIOS, installation proceeds smoothly but the operating system is only able to use 3 GB (as indicated by free -g).

    The motivation behind installing 64-bit was to be able to use 6GB - I already had 32-bit flavours of Ubuntu and of Windows 7 running without any problem (and they continue to run without problem irrespective of whether memory remap is enabled in BIOS).

    Please help me in using the whole 6GB in 64-bit install...

  2. #2
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    Re: 64-bit kernel panics if memory remap enabled in BIOS

    Interesting ...

    Does the panic happen at boot, or at some moment after booting?

    I would do this:
    - run memtest86 (it is in the GRUB boot menu) for a few hours to really test your memory
    - try 32-bit Ubuntu 12.04. As the recent Ubuntu versions use the PAE kernel, it will use all memory (6GB in your case)

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    Re: 64-bit kernel panics if memory remap enabled in BIOS

    I installed 64-bit because 32-bit OS was not using the full 6 GB...(the latest ubuntu 12.04 that is). Specifically, I used ubuntu business remix 12.04 32-bit.

    Ubuntu, Ubuntu Studio, Xubuntu all give the same error upon memory remapping enabled. The error is shown at boot time itself. Now that I have disabled the remapping, I have been able to install and have been using the computer non-stop for several hours post-install without any issues (except the main issue that I am not able to use all 6 GB)

    I shall leave memtest running overnight and post the findings.

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    Re: 64-bit kernel panics if memory remap enabled in BIOS

    Memtest running: with the memory remapping enabled, right?


    Ubuntu 32-bit can show & use more than 3.5 GB, as long as you have installed the PAE-kernel. I thought the Ubuntu installer would do that automatically. If not, you can post-install it.

    You can my script to get all info on your memory: BIOS, CPU, OS, PAE, etc:

    Code:
    wget http://www.appelboor.com/dump/check-my-hardware.py
    python check-my-hardware.py
    HTH

  5. #5
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    Re: 64-bit kernel panics if memory remap enabled in BIOS

    I shall try your script later tonight.

    memtest offers so many options! it ran fine with the default options selected and remapping enabled in BIOS. But it fails when I select some of the options in memtest (can't recollect which, will try again).

    Windows 7 memtest succeeds with memory remapping enabled in BIOS. Windows PAE forced mode does not result in more than 4G being recognized either.

    Both Ubuntu and Win7 are behaving consistently: both refuse to allow me usage of more than 4GB, both have memtest succeeding with default options and memory remapping enabled in BIOS.

    [edit: the 4GB RAM DIMM is Kingston Value RAM KVR1333D3N9/4G / 4GB / PC3-10600 / 1333MHz / DDR3 / 240 Pin / CL9 / Unbuffered DIMM]

    I don't know what speed the two DIMMs (one 4GB, the other 2 GB) are actually running at: the BIOS doesn't help me in that regard, let alone allowing me to adjust the speed, it does allow me to adjust latency, but if I tinker there, the system either doesn't boot (blank screen, no errors) or reboots. Every time I disable and re-enable memory remapping in BIOS, the first time Ubuntu reboots in the middle of boot-up, the second time onwards throws kernel panic.

    [edit: the latency I was talking about in above para is PCI latency, not RAM latency, sorry for that]
    Last edited by leo_m; June 23rd, 2012 at 01:07 AM.

  6. #6
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    Re: 64-bit kernel panics if memory remap enabled in BIOS

    You can my script to get all info on your memory: BIOS, CPU, OS, PAE, etc:
    The output is as expected:

    check-my-hardware.py - version: SJ 2012-06-03
    OK, you're root
    ANALYSIS:
    Total of physical memory modules found 6144 MB in 2 memory module(s)
    BIOS offers 3318 MB as usable
    Memory seen by OS 3261 MB
    BIOS version 06/10/2010
    CPU is PAE enabled
    CPU is x86_64 64-bit enabled
    OS is x86_64 64-bit

    SUMMARY:
    Memory difference between DIMM hardware and BIOS offering 2826 MB
    Memory difference between BIOS offering and memory seen by OS 57 MB
    Memory difference between DIMM hardware and memory seen by OS 2883 MB

    ADVICE:
    Your BIOS is not offering all of your physical memory. Try to update your BIOS, and/or enable 'memory hole rempapping / hoisting' in your BIOS to get more usable memory

    Finally: show more detailed memory info from lshw. This can take up to 30 seconds ...
    description: System Memory
    size: 6GiB
    description: DIMM SDRAM Synchronous
    size: 4GiB
    description: DIMM SDRAM Synchronous
    size: 2GiB

    Finished

    The 4GB DIMM is Kingston Value RAM KVR1333D3N9/4G / 4GB / PC3-10600 / 1333MHz / DDR3 / 240 Pin / CL9 / Unbuffered DIMM

    I don't know what to do - enabling memory remapping will result in Ubuntu not booting up...

    The max. supported memory for the computer is 8GB as per the specs. on the manufacturer's website...
    Last edited by leo_m; June 22nd, 2012 at 09:26 AM.

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