linux/Documentation/memory.txt
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   1There are several classic problems related to memory on Linux
   2systems.
   3
   4        1) There are some motherboards that will not cache above
   5           a certain quantity of memory.  If you have one of these
   6           motherboards, your system will be SLOWER, not faster
   7           as you add more memory.  Consider exchanging your 
   8           motherboard.
   9
  10All of these problems can be addressed with the "mem=XXXM" boot option
  11(where XXX is the size of RAM to use in megabytes).  
  12It can also tell Linux to use less memory than is actually installed.
  13If you use "mem=" on a machine with PCI, consider using "memmap=" to avoid
  14physical address space collisions.
  15
  16See the documentation of your boot loader (LILO, grub, loadlin, etc.) about
  17how to pass options to the kernel.
  18
  19There are other memory problems which Linux cannot deal with.  Random
  20corruption of memory is usually a sign of serious hardware trouble.
  21Try:
  22
  23        * Reducing memory settings in the BIOS to the most conservative 
  24          timings.
  25
  26        * Adding a cooling fan.
  27
  28        * Not overclocking your CPU.
  29
  30        * Having the memory tested in a memory tester or exchanged
  31          with the vendor. Consider testing it with memtest86 yourself.
  32        
  33        * Exchanging your CPU, cache, or motherboard for one that works.
  34
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