Ok, something is now clearing up for me. Yes, the uCAN2 board has a 10MHz crystal. Also, I guess I have been using the term EPROM loosely. As I mentioned in the previous post, I am intending to use a AT29C256, which is a 70ns Flash Memory device (PEROM). We'll have to program it outside the board since the board comes with a AT27C256-45, a 45ns OTP device (EPROM). Now I just checked the 80390 users guide and the MPU at reset defaults to a divide by 4 scheme, so the oscillator to machine cycle ratio is 4:1 (i.e. 4 osc. cycles to 1 mach. cycle). It also defaults to adding stretch cycles for MOVX memory, so a MOVX requires 3 machine cycles. I suppose this does not apply since MOVX is for data access only (right?). So, I want to replace a 45ns EPROM with a 70ns PEPROM. How do I determine if this new device is too slow? I also have to figure out how to move the application code from the PEPROM to RAM, and then how to start executing this code. Since the application code is in C, I'll have to conform to the C's run-time environment when placing it in RAM. Thanks again for your help.