The Museum of HP Calculators

HP Forum Archive 13

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Just wondering??
Message #1 Posted by Naim on 3 Aug 2003, 8:04 p.m.

I read the great by Mr Brogger about increasing the memory of a HP42S to 32K. My question is, has anyone found a use for the area where maybe a second RAM chip could be installed? Or is this for some other hardware that was abandoned at some stage. Just wondering [out loud]

Re: Just wondering??
Message #2 Posted by Randy Sloyer on 3 Aug 2003, 10:07 p.m.,
in response to message #1 by Naim

The 42S shares the same logic board with the 17B/17Bii and 27S. The vacant rom location was used only in the 17Bii for the different text strings to internationalize the calculator.

The detailed answer can be found here: and look toward the bottom for "XFCN".

Just wondering, too... Did you???
Message #3 Posted by Vieira, Luiz C. (Brazil) on 3 Aug 2003, 11:32 p.m.,
in response to message #1 by Naim

Hi, Naim;

I just want to know if you proceed with the upgrade and, in this case, if you succeed.

I am asking about this because I am trying to collect data about which 32K chip have people found to be usefull. I have found three different codes, each one with a different brand label, and in two cases, the donator was a non-working HP48G. Anyway, in two cases, I removed the chip from a deffective sound board. There were two chips in that board and I have already used them.

I have these RAM ID codes/numbers written somewhere, I just have to find the file. Have you taken note of yours, if any?

Another issue: as I see, the HP17BII has the same board and layout, but the HP42 uses a main chip with another package. The question is: would the HP17BII accept a 32KRAM chip as well? Not that I intend doing this, I just would like to know if its O.S. will address the extra 24KRAM. If the answer is Yes, then the HP17BII+ will need no further HW enhancement, only SW additions (if any) and a Kinpo-like design.

Best regards.

Luiz (Brazil)

Edited: 3 Aug 2003, 11:34 p.m.

Re: Hp17BII
Message #4 Posted by RR on 4 Aug 2003, 8:11 a.m.,
in response to message #3 by Vieira, Luiz C. (Brazil)

Speaking with experience. No the Hp17Bii cannot make use of the extra RAM space of a 32K chip. It will work (you then HAVE to configure just like the 42s), but it will not see the extra RAM. I never did the experiment on the 27s as I used the 17B for practice before I tackled a valuable 42s.

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