sorry for my noob question but what exactly does it do?
as far as i understood it disables the limit of the phone so it is able to use all its internal memory and not half... on the other hand it was said in the forum here that if i want to disable the himem i have to to reflash the rom because of a wifi driver... can anyone explain me more? i did a search here and didnt find...
Technically, highmem in the kernel refers to pages of memory that don't have a permanent virtual address mapping. The ARM architecture historically didn't have support for this, which is why the stock ROM with the 2.6.29 kernel didn't support that memory bank of the board. Why they decided to design it like this, I have no idea.
The reason you have to update the wifi kernel module when you disable himem, is because you disable himem by flashing a kernel without support for himem. The kernel and modules need to be closely matched, so they always need to be updated together.