Minimising system compiling time

[Peter Humphrey]

I'm running Gentoo on a dual-Opteron box and from time to time I decide
to recompile the entire system - absolutely everything on the disk apart
from a handful of binary packages. Needless to say, this takes a long
time, and I'd like to find the best setup for shortening it.

I assume that using a standard virtual terminal, not running X but using
the frame buffer, is the slowest because every scroll requires a redraw,
and there must be many thousands of them, maybe millions once I've built
a more complete system. So at the moment I'm using Terminal in XFce
4.2.1, which doesn't suffer that limitation but X does still need to
refresh the window a few times a second.

My questions are: 

1.  If I roll the window up so that only the title-bar shows, does this
reduce the overhead, or does X continue all the same work but just not
show the result?

2.  If the latter, should I set a particular window size to minimise the
overhead?

3.  Is there any better way of removing unnecessary overheads while
compiling several hundred packages? These include gcc, glibc, Xorg etc.
which do take more than a couple of minutes.

I suppose I ought to be able to answer the first two of those by peering
into the code of Xorg, but I'm sure it would be just slightly more
efficient to ask for opinions from those who know.      :-)

TIA

-- 
Rgds
Peter Humphrey
Linux Counter 5290.