Sounds like something that would benefit highly from putting your builds on a RAM disk. If you assume 100M SLOC @ 100 bytes per line you're looking at only ~10

Sounds like something that would benefit highly from putting your builds on a RAM disk. If you assume 100M SLOC @ 100 bytes per line you're looking at only ~10GB of RAM. That's only an extra $160 per build machine. (2x4GB DDR3 sticks @ $80 each) I shaved ~10 minutes off a ~15 minute build and unit test time by putting the SQL DB on RAM and the source tree in RAM. SQL was by far the biggest win. The source tree only saved us about 30 seconds. If you're on Windows just tick the Advanced Write Optimization box on your drive and all your writes will go to RAM. I think there is something similar on Linux. It sounds like you're the type of person who probably already knows this :) L2/L3 cache is absolutely huge but the biggest wins by far IMHO are battery backed write cache. The really shitty thing is most BBWC controllers use 50% of the cache as read cache by default which is a total waste IMO. I find about 10% read cache is optimal on the controller. If you can't afford SSDs and still need to guarantee consistency.