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<H2><A NAME="Additional Stuff"></A> <A NAME="s6">6. Additional Stuff</A></H2>
<H2><A NAME="ss6.1">6.1 Setting up MTRR's</A>
</H2>
<P>
<PRE>
** Note to Matrox video card owners **
If you have matroxfb compiled into the kernel,
chances are that your MTRR's are already set
up. You can probably just skip this section.
</PRE>
<P>Setting up your MTRR's can increase video performance quite
a bit in some cases, so it is a good idea to do it. First,
you need to make sure you have MTRR support in your kernel by
typing:
<P>
<PRE>
# ls /proc/mtrr
</PRE>
<P>
If it tells you that there is no such thing as /proc/mtrr, you
need to recompile your kernel with MTRR support (it is under
"Processor type and features" in menuconfig).
<P>
Once you know MTRR is working, you need to know the base memory
address of your video card, and how much video ram it has. The
easiest way to do this is to look at the output of X as it starts
up. Because the output usually scrolls off the screen and is
lost when it switches to a different tty, you need to redirect the
output of X to a file (xoutput) so you can go back and look at it
to get the needed values. This can be done by typing:
<P>
<PRE>
# startx 2> xoutput
</PRE>
<P>
The line having the needed information is probably somewhere
towards the middle of xoutput, and should look something like:
<P>
<PRE>
(--) SVGA: PCI: NVidia Riva TNT2 rev 17, Memory @ 0xee000000, 0xe2000000
</PRE>
<P>
Once you have located that, write down the last memory address, in
this case 0xe2000000. Depending on your hardware, you may or may not
have multiple memory addresses shown, so don't worry if yours looks a
little different. With this information recorded, you can delete
xoutput.
<P>
Next you need to create a new MTRR. In order to do that, you have
know how much ram your video card has in hex. Here are some common
values:
<P>
<PRE>
4MB -- 0x400000
8MB -- 0x800000
16MB -- 0x1000000
32MB -- 0x2000000
</PRE>
<P>
To add the MTRR, type:
<P>
<PRE>
# echo "base=0xe2000000 size=0x2000000 type=write-combining" >| /proc/mtrr
</PRE>
<P>
Substituting "0xe2000000" and "0x2000000" with the base address and amount
of video ram specific to your system.
<P>
Now you should have MTRR set up, and just to make sure, type:
<P>
<PRE>
# cat /proc/mtrr
</PRE>
<P>
And you should get output that looks remotely similar to:
<P>
<PRE>
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
reg01: base=0xe2000000 (3616MB), size= 32MB: write-combining, count=1
</PRE>
<P>
Again, the number of entries will probably be different from these,
don't sweat it.
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