If you use anything except a 2MB double sided SIMM, you'll only get 1MB chip memory instead of the expected (maximum) 2MB.
The correct SIMMs can be hard to find. I got sick of constantly trying to locate and purchase used SIMMs in unknown condition, and fixed the problem by designing my own.
I've got stock available if you can't find them elsewhere:
http://amiga.serveftp.net/inventory.xgi - see part number SIMM72, 2MB DS
