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#1 2006-01-22 00:52:35

From: USA
Registered: 2004-06-25
Posts: 533

MTRR support

I'v been using arch for over a year but I'm still a newbie with alot of the
techy linux stuff, so posting this in the newbie catagory seemed
apropriate. I found alot of info on the web for setting up MTRR but not
much info on the specific mem addresses to use or the disadvantages
of using MTRR.

I do alot of cad programming on my box which isn't directly related
to linux in general other than set up of custom software. To increase
performance I needed to set up MTRR suport. Can anyone tell me
if I did this correctly?

I have a dual monitor configuration on two seperate graphics cards setup
as two independant screens. A gforce3 64mb agp card and a gforce4
64mb pci card.

This is in my Xorg.0.log file pertaining to my graphics cards....
(--) PCI:*(1:0:0) nVidia Corporation NV20 [GeForce3] rev 163, Mem @
0xfb000000/24, 0xdc000000/26, 0xe2580000/19, BIOS @ 0xfa9f0000/16
(--) PCI: (2:9:0) nVidia Corporation NV17 [GeForce4 MX 440] rev 163,
Mem @ 0xfd000000/24, 0xe8000000/27, 0xf2780000/19, BIOS @

I was confused about which memory address to use when configuring the
MTRR's. When using the last one just before the BIOS I kept getting a
error so I used the ones 2nd to the last from the BIOS.

0xdc000000 for my gforce3 card
0xe8000000 for my gforce4 card
and using 0x4000000 equaling 64mb

In kde auto start I created a executable to run these commands at kde
start. I'm not sure if this is the best way of doing this although I
normally run graphics hungry software from xterm login, so I
type this in manually....

echo "base=0xe8000000 size=0x4000000 type=write-combining" >|
echo "base=0xdc000000 size=0x4000000 type=write-combining" >|

Then after doing a # cat /proc/mtrr
I get the following....

reg00: base=0x00000000 (   0MB), size= 512MB: write-back, count=1
reg01: base=0xe8000000 (3712MB), size=  64MB: write-combining,
reg02: base=0xdc000000 (3520MB), size=  64MB: write-combining,

My questions are.... Did I do this correctly?
Does this seem like a correct output from # cat /proc/mtrr?
Are there any dissadvantages to using MTRR and if so can I optimize
it better to lesson the dissadvatages?

Since I usually run my cad software from a Xterm login to save resources
I was wondering if I can add the MTRR lines to my grub/menu.lst so I
don't have to type them in each time after boot when working from

Thanks tons for any input or advice anyone can give me.


-- archlinux 是一个极好的 linux


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