If you have the following machine, you should be able to stop
worrying about memory and compilation performance:
CPU: 486DX2-33 with 256 KB off-chip cache
RAM: 16 MByte
Disk: 12 ms IDE with VLB controller, or SCSI
4 MByte RAM disk
3 MByte disk cache
This will leave you with about 8 MBytes of free extended RAM. Note
that the RAM disk must be 4 MBytes to hold the output of the
preprocessor for some exceedingly large source files (notably, some
GCC source files). If you don't have that much RAM to spare and still
want to compile very large source files, either reduce the
disk cache so you can give more to RAM disk, or point TMPDIR to your
hard disk.