The Emulator III Uses 30 pin SIMM1 @120ns or faster . Original units were shipped with 4Mb & can be expanded to 8Mb with (4) SIMM1s. Later production models came stock with 8Mb (not expandable). The only way to tell is to check memory remaining. Memory is installed in groups of 4 SIMMs and is displayed in Megawords which equals 1/2 the amount of Mb.