Messages in this thread | | | Date | Wed, 12 Jun 2013 23:33:26 +0200 | From | JA Magallón <> | Subject | Re: Accessing more than 2GB of memory with a 32 bit kernel |
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On 06/12/2013 10:10 PM, Rik van Riel wrote: > On 06/12/2013 12:54 PM, Simon Brown wrote: >> Hello, >> >> For the sake of an old prototype peripheral I'm using a non PAE 32 bit >> x86 kernel and I'm having trouble accessing memory above 2 GB. The >> system has 4GB installed and all is well with a PAE kernel. >> >> I'm obviously expecting to lose some memory due to memory mapped devices >> but I wasn't expecting to lose 2GB. Instead I'm suspecting a BIOS bug. >> The system reports: >> free -m >> total used free shared buffers >> cached >> Mem: 2012 491 1521 0 40 >> 277 >> >> The mtrr table looked odd so I enabled sanitisation: >> [ 0.000000] original variable MTRRs >> [ 0.000000] reg 0, base: 2GB, range: 2GB, type UC >> [ 0.000000] reg 1, base: 0GB, range: 4GB, type WB >> [ 0.000000] reg 2, base: 4GB, range: 2GB, type WB >> [ 0.000000] total RAM covered: 4096M >> [ 0.000000] Found optimal setting for mtrr clean up >> [ 0.000000] gran_size: 64K chunk_size: 64K num_reg: 2 >> lose cover RAM: 0G >> [ 0.000000] New variable MTRRs >> [ 0.000000] reg 0, base: 0GB, range: 2GB, type WB >> [ 0.000000] reg 1, base: 4GB, range: 2GB, type WB >> >> I don't understand the gap in the new table. > > Check the e820 table. Chances are the BIOS is reserving 2GB to > map various devices (especially video cards) below the 4GB limit. > >
Acording to manual, that mobo has an option to "Memory remap feature" in BIOS that looks like that...
-- J.A. Magallon <jamagallon()ono!com> \ Winter is coming...
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