It wouldn't really surprise me if different firmwares produce different fan speeds. New features will each add in their own CPU demands, while code optimizations and algorithm improvements will possibly reduce those in subsequent releases. The OS workload, as a whole, quite possibly varies with every release, with some being more demanding on the hardware than others.
Consider DVD upscaling throughout the versions. The 1.80 update, which added network streaming and high-quality DVD playback, had many users complaining of increased fan noise. On a superficial level, this makes sense: adding more CPU intensive features causes an increase in chip temperatures, which then may then cause an increase in fan speed. Subsequent firmware versions reduced that workload, in DVD playback especially, through better algorithms and code optimizations.
"In 1.80, it was almost full load when upconverting a DVD, but not now due to optimization" (source) . There were also improvements in BD playback, and, one would think, in other areas "under the hood" as well. For me at least, this meant that firmware (2.20) made my PS3 almost dead silent, though I cannot rule out other factors as the cause (such as changes in ambient room temperature or usage habits).
So, there we go. Remember, there doesn't have to be a huge variation to produce changes in fan speed. Maybe you are just at the threshold right now, and maybe a slight increase in processor demand would send you into another gear. Lord knows.
In-game XMB sounds like a demanding background process, doesn't it? Maybe that feature (2.40) will send
your console into that dreaded 3rd gear? Maybe you want to forget this update, and wait till 2.41 or 2.42 (a hopefully stable release?). Well, I guess we will find out. It will be a nice way to "test" my theory.
I, on the other hand, will wait a few days before installing that update. You all who so dearly and naively trust Sony, please tell me if 2.40 does indeed increase your fan speed. I will be waiting for initial reports, just as I have done for every other major update.
There is no going back once you have installed an update; so I prefer to be safe, rather than sorry. Never know what you will get with these fresh new Sony-created firmwares.
