inconsistent mounting

I have two 1TB and one 2TB drive in this workstation. The two that don't 
have an OS on them are purely storage and every time I reboot I have to 
mount them manually.
The reason being is that they often turn up in different locations after 
the reboot.
For example the 2TB may appear on /dev/sda or perhaps /dev/sdg or /dev/sdf

I would have thought one would have to physically change the 
sata-lead/sata-port on the motherboard for this to happen, but it seems 
not.
Something in the BIOS perhaps?

This random allocation is what prevents me from adding the mount points 
to fstab for auto-mounting the storage drives.

any ideas?

chris