I actually determined this by removing one and rebooting the Mac to see w hich one showed.
Bank 0: Closes to motherboard
Bank 1: Closest to you when open and viewing it
This also makes it easy to diagnose which is which, just take one of the memory chips out and plug it back in and reboot, look at it again and it will show you which slot is empty. Thats also a good way to tell if one is bad or not, just put one in at a time as the Mac will still run fin with just one memory chip in it.