FreeBSD 5.x was the learning curve for SMP (and also brought in a lot of other technologies such as power control); there was a tremendous amount of changed cod

FreeBSD 5.x was the learning curve for SMP (and also brought in a lot of other technologies such as power control); there was a tremendous amount of changed code. For some people it worked fine; for many it was pretty rough. The decision for 5.x was to gamble that single-core systems were going to become less important than multi-core systems, and that FreeBSD should push to optimize for the latter. Around the 7.0 timeframe, that promise finally started paying off. By that time, performance and stability on SMP were on a par with what 4.x had had on single-core. Let's put it this way: there were no tears shed when 5.x went EOL :-) (fwiw, the last maintenance release of 5.x was in 2006.) For anyone whose last experience was 5.x, 8.1 will be a difference of night-and-day.