One of my 41's doesn't like modules in port 4

[Monte Dalrymple]

(05-09-2016 06:05 AM)damaltor Wrote:  That might be. The card reader works fine on an other HP41 though, so the error is to find in the 41C. Maybe the ISA driver of the 41 is broken...

Also, shouldnt that be a problem only AFTER switching the device on? The Sound immediately comes up when i plug the reader in, not when i switch on the calculator.

A peripheral device can wake up the 41C CPU by pulling the ISA line High while the CPU is asleep. That's why I think that problem has something to do with that signal.