Can the HP 41 Read HP 65 Programs

I continue to try and debug/fix my newly acquired 65. If I knew the 65 can write a program (to be read by the 41), it might help me narrow down some things.


IIRC, the HP-41 can read HP-67/97 cards; but no HP-65 cards. I think the recording format is the same, but the data (op codes) are possibly meaningless... However, trying will not hurt.


The HP-65 used six bit op codes to store its programs; the HP-67 and 97 used 8 bit codes. No machine after the 65 could read its card data (programs or registers). Sorry.

Trivia - the 65's program storage was a dynamic shift register so the program was constantly circulated around same. There was no addressing for the data. The way a particular instruction was found was that a particular index value (all zeros if I recall) was stored *once* in the register. When that came by the read circuit, a counter was started. When the appropriate number of values clocked by after that, the desired value was read.

Of course, if more than one index value ended up in the program store the data read would be randomly chosen as so many values after either one. I'm still boggled that one of the old HP-65 Users Club members figured this all out on his own without any logic analyzers, oscilloscopes, internal documentation, etc.

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