512MB PC133: One Module that uses two banks?

I have a Promise SX4000 RAID controller, and if you are not familiar with it, the cache is just a PC133 DIMM. The controller supports a single DIMM up to 256MB, but according to one person here: http://www.newegg.com/app/ViewProductDesc.asp?description=16-102-012&depa=0&section=3 you can use a single 512MB DIMM that uses two bank but occupies only one slot. I like the idea of having 512MB of cache and want to try this, but I can't find any PC133 that works in two banks but uses one slot. Does anyone know of any particular modules or have any sugestions? Thanks

Correct me if I'm wrong, but doesn't 2 banks = double sided? I don't see what the big deal is.

I am pretty sure also that double sided ram = 2 banks. That is what my double sided ram shows up in my old AMD K6-2.