Here's another story: I was optimizing the performance of a small, in-house x86_64 OS on a specific benchmark. I spent many months finding and removing/improvin

Here's another story: I was optimizing the performance of a small, in-house x86_64 OS on a specific benchmark. I spent many months finding and removing/improving bottlenecks. Once the performance was similar to competing OSes, the measurements from my performance experiments were varying by 30%! This was surprising because the benchmark was simple and the performance of competing OSes was completely stable. Well after three or four days of frustration, I discovered that the problem was our test hardware: for whatever reason, immediately after BIOS POST, any memory loads executed for the next 10 seconds were 30% slower than memory loads executed almost exactly 10 seconds after BIOS POST. Initially I was shocked, but this may make sense -- it seems plausible that hardware manufacturers would run initialization code in the background resulting in quicker boot times. Anyway, after we figured that out we simply waited 10 seconds after POST before we ran any experiments. I'm curious how common this slow-for-the-first-10-seconds thing is with other x86_64 machines. Edited for clarity.