Re: Mystery HP41 CX Message #2 Posted by Winfried Maschke on 29 Aug 2007, 7:03 a.m., in response to message #1 by Dave Colver
Most likely the PCBs of the two modules are build inside the 41. The switch connects the ISA-line of the modules to the calculator.
If the switch is turned on, the build in module is hardwired to one of the HP41 ports and you cannot use this port for another ROM module.
Beside some others I did such kind of mods for many people in europe. You could even buy a PCB to build in 4 modules. Here is a picture..
There ist no way to upload other software as it is a hardware mod with ROM modules.
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