Setting up MTRRs for 4096MB RAM

[Corin Hartland-Swann]

Hi there,

I am trying to set up a machine using the Tyan Tiger LE motherboard, and
ServerWorks III LE chipset to use 4096MB RAM. I'm using kernel 2.4.7 with
CONFIG_HIGHMEM4G.

I know that I have to set the MTRR's up to extend the cacheable memory
area, but can't work out how to set it up.

I tried the following:

  # echo "disable=1" >| /proc/mtrr
  # echo "disable=0" >| /proc/mtrr
  # echo "base=0x0 size=0xFFFFFFFF type=write-back" >| /proc/mtrr
  mtrr: size and base must be multiples of 4 kiB
  mtrr: size: 0xffffffff  base: 0x0

Which doesn't make any sense. So I tried for 3G RAM:

  # echo "base=0x0 size=0xC0000000 type=write-back" >| /proc/mtrr
  mtrr: base(0x0000) is not aligned on a size(0xc0000000) boundary

And then for 2G RAM:

  # echo "base=0x0 size=0x80000000 type=write-back" >| /proc/mtrr

Which works perfectly. What gives?

Also: the instructions in Documentation/mtrr.txt says to use ">|" instead
of ">" (under bash, at least) - what does this accomplish?

Thanks,

Corin

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