And so I give you ...
There is a good chance that this STK12C68-5 chip can be popped into an
MP-1, eliminating the battery. (As you can see, it has an "STK" part
number: this was a Simtek part.)
I got my hands on two of these chips. They do not actually fit because they are not the "wide" 28DIP expected by the socket in the MP-1, but the "skinny" one. (Skinny dip, haha).
This is actually a good thing, because I need to make a daughterboard adapter anyway; based on studying the datasheets, it's obvious that a few external components are needed (not only the capacitor) and a slight interfacing modification: one pin that is connected now is going not to be connected to the corresponding socket on the MP-1's board, but instead pulled up to +5V through a resistor.
Because chips are skinny, it will help make the daughterboard smaller.
I hope this works out; wish me luck!
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