Drawing to the moniters is really slow because all graphics calls are sent
to the moniters via the FIFO named pipes. I guess you could rewrite the parts o
f the code you need to speed up such that they make Xwindows calls directly. Ho
wever, in doing so, you make the code Xwindows-dependent and may have to hack t
he code everytime a new GRASS version is released. [Plus, all the GRASS authors
will be mad at you 
]
If you have the Grass 4.1 Programmer's Manual, see page 183 - it explains i
t all.
Finally, what do you need to speed up - d.rast? If so, starting looking in
the files GRASS/src/libes/D/Dcell.c & GRASS/src/libes/display/raster.c & raster
2.c
Hope this helps some.
Sharif Razzaque
sharif@lams.msd.lmsc.lockheed.com