Neil, that means your hardware is fine. If you have the ports configured (i.e. unchanged) as in the monitor, CPM3 banked mode switching should be fine. Read my write-up very carefully however. Is the MAKECPM submit file goes fine then I suspect something in the boot/sector loading. Does your non-banked version work fine? John From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of nbreeden I've been able to verify that the bank swapping via ports 0xD2 and 0xD3 work as expected. I wrote a unique pattern into each of the 64 16K banks then read each page back using both 0xD2 and 0xD3 (0x0000-0x3FFF and 0x4000-0x7FFF). I'm confident that the banked memory is working as expected. I'm not sure where to go next with this. Is there a list of jumper and DIP switch settings / ports used for the base configuration that the banked CPM is setup to use? For the serial versions which S-100 card is being used to provide the serial port? -Neil -- |