AIOServer process question

Hi
I've been trying to learn a bit more about AIOServer processes and how my company administers them, one question i have is, while checking, most of my servers show a memory overhead of about 448 k per aioserver process (nmon -A) however i have found a few with figures of 67 or 56k. Most servers are running 5.3 tl 10 with a few running 6.1 but this isnt connected to the differences.

While the majority are 448 is this a configurable value ?, if so is there any documentation or advice on what affect the size has on the processes performance ?

Cheers all

Phil