HP-42S Versions, ROMs and Bugs


Can anyone give me some details abobut 42S versions, date codes, ROMs and bugs?

I would like to buy one and am not too sure which to go for (if I have a choice).

I prefer the older keyboard feel but dont want any serious ROM bugs, so any info owuld be appreciated.


Rom bug list is here:


IMHO, I would go for an early Singapore unit (1990-1992) because these have:

1. No double lens to collect dirt.
2. Good keyboard feel.

Good hunting.


I have a program called "FAST" in my calculator that changes the speed constant to run the HP-42S at 2X speed.

This only works with the first year or so of HP-42S machines.



for more information.


hurra, it work's on my machine.

More of these hidden features !!!

BTW is it true that this acceleration
also speeds up the energy consumption ?

happy programming........Erich N.


You bet... Nothing comes for free when energy is the issue.


If this is the money, I've to pay....so be it.

happy programming...........Erich N.


You can also set the HP-42S to run as slow as possible too. You wouldn't notice it when doing calculations, but it would really really lengthen the battery life. :-)

Later model HP-42S calculators can do this speed up MANUALLY by entering the debugger and changing the value as indicated, but they must do it every time the calculator is turned on.

The good thing about the early HP-42S is that it can use this program. I made sure that I used the program by putting "SF 11 ; OFF" as the first 2 lines. Then when I turn the 42S off, the first thing it does when I turn it back on is finish running the fast program.

Always at 2X.

Really makes some of the longer HP-41 style programs, such as Othello, really nice to use.


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