They require 4 meg SIMMs (70ns or faster) installed in pairs. They should be 8 chip SIMMS - not the composit 2 chip type. We use OKI here and I have also had success with NEC and Mitsubish. You can install up to 8 SIMMs for 32meg total. Also, there is a special tool that you MUST have to remove any SIMMs from the SampleCell. The SIMM sockets are a special locking type.