Speeding up PPro's and PII's (was Mmap device performance)

Benjamin Redelings I (bredelin@UCSD.Edu)
Thu, 11 Dec 1997 10:39:43 -0800

In order to make PPro's and PII's perform at their full performance, you
need to enable write-combining on the linear frame buffer. You may have
a driver in win95 that does this automagically, but I need to turn in on
manually. To do so in win95, I use fastvid or ctppro. In Linux you use
the module 'proform.o'. You can get all of these utilities at the 'Fast
Graphics Site', or by searching the web for them.

Proform sets a MTRR (Memory Type Range Register) to specify that a
certain amount of memory (2MB in my case) at a certain address (e0000000
in my case) is write-combining. I modified the source code so that
those are the defaults, but you can specify them on the command line.
There are (I think) 8 variable MTRR's so you could theoretically have 8
linear frame buffers,though I'm not sure exactly how you would do
it...shouldn't be too hard.

Anyway, after building proform (and making my linear frame buffer the
default so I don't have to specify it as an argument to the module) I
just do 'modprobe proform.o enable=1'. Actually, I put that in my
/etc/modules file, I think.

Good luck,
-BenRI