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Alex Schuster <wonko@×××××××××.org> schrieb: |
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> So I installed another 4 GiB RAM into a Gentoo amd64 system that had 4 GiB |
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> already. But it still sees only 4 GiB, not 8 GiB: |
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> |
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> leela ~ # uname -a |
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> Linux leela 3.6.11-gentoo #3 SMP Mon Feb 4 15:37:48 CET 2013 x86_64 AMD |
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> A6-3500 APU with Radeon(tm) HD Graphics AuthenticAMD GNU/Linux |
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> |
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> leela ~ # |
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> free -m total used free shared buffers cached |
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> Mem: 3688 3269 419 0 108 1050 |
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> -/+ buffers/cache: 2110 1577 |
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> Swap: 2047 54 1993 |
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> |
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> Huh? Any idea why this is? The BIOS shows the full 8GiB, and lshw finds |
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> it. dmidecode shows that 8G should work: |
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Two ideas: |
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An addon card is blocking the usage of RAM above 4 GB. See if your BIOS is |
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enabled for 64 bit systems and if everything will map above 32 bit address |
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space. Usually there are BIOS configuration sections like "resource |
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allocation", "memory hole", "resource relocation", or similar - you get the |
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idea. |
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My second idea is: Look at dmesg if there are errors from MTRR which allow |
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the kernel to only make use of 4 GB of RAM. Usually, the kernel tries its |
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best to adjust MTRR to make as much use of RAM as possible with lower |
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priority to memory access performance. If you tuned MTRR manually before, |
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you are likely to be running into memory issues. Also, check if there is a |
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BIOS update available. Sometimes this is needed to correct MTRR settings so |
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memory becomes avaiable to the OS. Also look at your kernel options |
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regarding MTRR support / defaults. |
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These kernel options may help you: mtrr_gran_size, mtrr_chunk_size |
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E.g., I have 16 GB installed and adjusted MTRR settings to allow using write |
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combining (which cannot be enabled by the kernel with the default MTRR |
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settings from BIOS). But that came with the downside of loosing around 1 GB |
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of usable RAM. |
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-- |
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Replies to list only preferred. |
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