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Re: mtrr funnies

Wolfgang S. Rupprecht wrote:
I've got a motherboard with a fairly new chipset (Asus M3A78T
w. AMD/ATI 790GX) and I'm seeing a funny MTRR setting.  I have 8GB
memory and am running a 64-bit kernel, but I'm only seeing ~4GB
mentioned in the MTRR's.  Is this a bug?  Do I need to add the upper
4+GB by hand?

    $ cat /proc/mtrr
    reg00: base=0x00000000 (   0MB), size=2048MB: write-back, count=1
    reg01: base=0x80000000 (2048MB), size=1024MB: write-back, count=1
    reg02: base=0xc0000000 (3072MB), size= 256MB: write-back, count=1
    reg03: base=0xd0000000 (3328MB), size= 256MB: write-combining, count=1

It does seem like the kernel sees the whole memory, at least at times,
but it isn't clear if that high memory is being cached the right way.

    Oct  7 10:54:30 poblano kernel: Memory: 7678940k/8650752k available (2699k kernel code, 184672k reserved, 1485k data, 980k init)


On the AMD's I remember one of the AMD experts mentioning that the >4GB memory stuff is automagic so is not listed as a MTRR at all. It is just there.

Does "cat /proc/meminfo" and top both show around 8GB like expected?


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