Kernel Task and RAM

Question

Hello again, Apple Friends.
Recently I have noticed that kernel_task in Activity Monitor is running at anywhere between 60MB and 200MB of RAM, which is really slowing things down. I have searched on the discussion boards the past few days and have found similar posts related to MB Air and old Powerbooks, but nothing about iBooks.
The kernel_task process will run, using up lots of RAM, even if I have no apps running whatsoever. If I let the iBook idle, over the course of 15 minutes (nothing running) it goes from 60MB to 150MB, with anywhere from 47 to 60 threads. That's when idling!
What I've tried to eliminate: (none of the following are the problem)
Firefox 3
any and all items / drivers in my login startup (the only ones I have not tried removing are those that are Apple)
resetting PRAM (did this)
Repaired disk permissions (did this 2 or 3 times, and each time after checking other items above).
I do not regularly have any peripherals attached, and the problem has existed without peripheral devices. I did get new RAM added a few months ago (I went from 516MB - or something like that - to 1.25GB) and I am wondering if this is part of the problem? But I have only noticed the problem recently. I'm not receiving any kernel panics, and so I'm not too worried, but I am really wondering if there is something amiss I should be worried about. And when I start using other major-memory apps (like iTunes, for example), the kernel_task process goes wayyyyy up (to 250MB or more).
I should add that I have also tried all suggestions listed in this thread, but to no avail.
Does anyone have any ideas?

Answer 1

Well, I have discovered something interesting. After your advice, BD, I tried a few things. First of all, after login, just leaving the computer idling, the kernel task does increase gradually over the course of 15 minutes -- I have tested this 3 times and it usually starts at around 60MB from login and creeps up to anywhere from 75MB to 120MB at the end of 15 minutes.
But then I wondered if it was somehow connected to my login account. I realized this problem only occurs under my main account. This account is not an admin account (I have a separate one for that). I logged in with 3 different accounts (boyfriend, Visitor, and my brother's) and none of them even had the kernel task running on login. Yet under my main account, it is running, starting at 60MB and with 47 threads.
Is this unusual? My next trick is to leave it idling for 30 minutes after login to see how much the memory use increases. But I am really curious now.