Memory is segmented on the Picasso via a single jumper on your video card.
The FOUR chips to the right of the blitter (closest to the VGA connector) is the jumper you need to be sure is OPEN. In other words - not connected. If that jumper is "jumped", then you are running your card in segmented mode. Not cool.
BTW: all of this segmented garbage is rubbish if you are using 32-bit ram (non Zorro II memory cards). There is no need to worry about segmentation if your RAM usage is above typical memory allocation of the Zorro II standard.