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[ccp4bb]: Speed-up O for Linux!

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Dear All,

I came across of one very interesting tweak (see www.lunix.com) with which
you can gain
some more performace from your X. Here it comes:
Improve your X11 performance.
  by - Skill: A - Jul 27, 1999
(this tip requires you to be using a pentium pro or better and have mtrr
enabled in kernel)
cat /proc/pci

VGA compatible controller: S3 Inc. ViRGE/DX or /GX (rev 1).
Medium devsel. IRQ 7. Master Capable. Latency=40. Min Gnt=4.Max Lat=255.
Non-prefetchable 32 bit memory at 0xf8000000 [0xf8000000].
And we see our video card, now we can speed up writes to the device by
combining writes to teh same memory area in a technique known as write

The command to enable write-combining to a 4 meg area starting at 0xf8000000
echo "base=0xf8000000 size=0x400000 type=write-combining" >> /proc/mtrr

Now in /proc/mtrr we see the following new line:
reg02: base=0xf8000000 (3968MB), size= 16MB: write-combining, count=1

If we need to disable this mtrr later the command is:
echo "disable=2" >> /proc/mtrr
(the 2 comes from the reg02 in /proc/mtrr above)
I've done it with my Dell I7K laptop (ATI LT RAGE RPO chipset). Fired up O
and run the spin on the molecule - the performance increased by 100% !!! I
have XFree86 3.3.6 and I think that this tweak is already impemented in
XFree86 4.0. Anyway, try it and try not to fall out of your chair ;-)


Dr D. Y. Chirgadze
Research Associate
Department of Biochemistry
University of Cambridge
80 Tennis Court Road
Old Addenbrookes Site
Email: dima@bioc.cam.ac.uk
Tel:   +44-1223-766029
Fax:   +44-1223-766082