You have a TI-85, correct? I am fairly positive that all cpu's in 85's are _Zilog_ Z80's. Take a look on www.ticalc.org on the section about the different calculators, and read about the 85 hardware. Maybe it will help, I don't know. (but putting more RAM directly into the calc would be quite an accomplishment :) Hope it works out well (for your sake and my sake ;), Mike Matz