> Compiles are generally HDD bound once you hit 4+ cores. If I do make clean / make / > make clean / make on Fedora the second one takes about 20 seconds start to finish > because the entire source tree's already in RAM. I'll time a completely cold run > sometime though.
Hm, I timed my compiles after building my system by creating a RAM disk and copying the entire MAME tree to it before invoking the compile, and my time was around 2 and a half minutes. This does not differ significantly from my 'cold' compile time after a fresh boot with no RAM disk involved. So in my experience, the HDD is not the limiting factor, at least not with a 6 core Phenom II; maybe it is the limiting factor for your Sandy Bridge, though. At a 20 second full compile I can certainly see that being the case.
BTW my HDD is an Intel X-25M G2, and I wouldn't be surprised if a platter HDD would be the limiting factor if that's what someone has.
So to recap:
Sandy Bridge w/SSD or RAM cache > Phenom II w/SSD or RAM cache > most anything else with SSD or RAM cache > anything with HDD
EDIT:
Are you *sure* about that 20 second compile time? Thinking about it, that's just incredible. I mean that's 7.5 times as fast as my Phenom II. If you told me that the Sandy Bridge compiled 2x as fast as the Phenom II, I'd raise my eyebrows a little bit but still believe you. But 7.5x as fast? That's really hard to believe, unless my system is somehow misconfigured. But I did compare my system against an Intel Xeon E5540 that I have access to, and my Phenom II system as about 10% - 20% faster, which matches up with other benchmarking results I've found out there. So I think my Phenom II results were good. I just don't understand how a Sandy Bridge even at 4.8 Ghz would be 7.5x as fast as a Phenom II at 3.0 Ghz. If the Sandy Bridge were, clock for clock, 100% faster than the Phenom II per core (and that is quite generous), then I would expect the Sandy Bridge to be 2.13x as fast as the Phenom II. Even if the Sandy Bridge somehow magically added 2 real cores, it would only be 3.2x as fast. I just don't understand where a 7.5x speedup is coming from.