memory.txt

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    1 There are several classic problems related to memory on Linux
    2 systems.
    3 
    4         1) There are some buggy motherboards which cannot properly 
    5            deal with the memory above 16MB.  Consider exchanging
    6            your motherboard.
    7 
    8         2) You cannot do DMA on the ISA bus to addresses above
    9            16M.  Most device drivers under Linux allow the use
   10            of bounce buffers which work around this problem.  Drivers
   11            that don't use bounce buffers will be unstable with
   12            more than 16M installed.  Drivers that use bounce buffers
   13            will be OK, but may have slightly higher overhead.
   14         
   15         3) There are some motherboards that will not cache above
   16            a certain quantity of memory.  If you have one of these
   17            motherboards, your system will be SLOWER, not faster
   18            as you add more memory.  Consider exchanging your 
   19            motherboard.
   20 
   21 All of these problems can be addressed with the "mem=XXXM" boot option
   22 (where XXX is the size of RAM to use in megabytes).  
   23 It can also tell Linux to use less memory than is actually installed.
   24 
   25 See the documentation of your boot loader (LILO, loadlin, etc.) about
   26 how to pass options to the kernel.
   27 
   28 There are other memory problems which Linux cannot deal with.  Random
   29 corruption of memory is usually a sign of serious hardware trouble.
   30 Try:
   31 
   32         * Reducing memory settings in the BIOS to the most conservative 
   33           timings.
   34 
   35         * Adding a cooling fan.
   36 
   37         * Not overclocking your CPU.
   38 
   39         * Having the memory tested in a memory tester or exchanged
   40           with the vendor. Consider testing it with memtest86 yourself.
   41         
   42         * Exchanging your CPU, cache, or motherboard for one that works.
   43 
   44         * Disabling the cache from the BIOS.
   45 
   46         * Try passing the "mem=4M" option to the kernel to limit
   47           Linux to using a very small amount of memory.
   48 
   49 
   50 Other tricks:
   51 
   52         * Try passing the "no-387" option to the kernel to ignore
   53           a buggy FPU.
   54 
   55         * Try passing the "no-hlt" option to disable the potentially
   56           buggy HLT instruction in your CPU.

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FreeBSD/Linux Kernel Cross Reference sys/Documentation/memory.txt

FreeBSD/Linux Kernel Cross Reference
sys/Documentation/memory.txt