(Curiosity killed the cat so maybe I should just leave this alone but ... )
That number looks to be half the clock speed of the processor (number of cycles in half a second)
Just a stab that the 243000000LL / 128 is just a convenient way to calculate a second then the 2 * 60 could mean every 2 minutes it's being read.
Anyone with a problematic drive know exactly how long their drive takes to go to sleep?
First I wanna ask you what does "curiosity killed the cat" means? I hear it a lot but where I come from we're not familiar with this story!
Anyway back on topic and to answer your question, I believe my hard drive goes to sleep mode if it doesn't read any data for like 30 seconds or so "the time needed to beat level 2-1 Crazy Drift in Crazy Taxi because I always use it for testing"!
This one: