HP 10B continuous memory

Hi all,

I just acquired an HP 10B, serial no. 3246S05152 made in Singapore. This is the original model algebraic financial calculator.

It passed the keyboard and display self tests as described here http://www.keesvandersanden.nl/calculators/selftest_pioneer.php

I found that every time I switch off the unit, it will display a "0" i.e. it does not have continuous memory. Can anyone please confirm this model has no continuous memory?

I thought that all HP models after the HP 25C featured continuous memory.

hpnut in Malaysia

Edited: 31 May 2011, 10:54 a.m.


Yes, the HP-10B definitely has CMOS (continuous) memory. If the contents of memory are not being retained when the calculator is switched off, then probably power is not reaching memory. This can be due to component failure or a bad circuit connection.

Edited: 31 May 2011, 11:55 a.m.


I believe it's correct that it does not remember the last displayed number. However, it does keep all the memory registers and financial registers. IIRC the 20S is the same. I do not have them with me, but will check when I get home tonight.



What you see is normal. Stack (or rather, Display) contents are not preserved on the 10B and 20S, as Bart states. Registers and program memory (on the 20S) are preserved. (I just turned on my 10B and 20S for the first time in several years, they still have what I left in them from that time.)

Store something in Register 3, turn the 10B OFF, then back ON. If Register 3 still has what you stored, its CM is working.

FWIW, I think the HP-41C and the Voyagers were the first HPs to preserve everything including the stack. I don't recall that *any* LED HP calculators with CM preserved the stack. I know that the HP-19C, -29C, and -34C don't, so I suspect the 25C that you cited doesn't either (but I don't own one to test). Perhaps the LCD 10B and 20S Pioneers don't preserve the display (and internal stack) the way RPN Pioneers preserve their stack is due to them being non-RPN algebraic models. The HP 10bii doesn't preserve the display either. What about the new HP 10bii+? The HP 30b in algebraic mode *does* preserve the display.

Certainly some other HP calcs contemporary to the 25C do not have any CM. Stuff like the HP-67, -97, etc.

Edited: 31 May 2011, 1:46 p.m. after one or more responses were posted


The HP-19c and HP-29c do preserved the display (x stack register), however, they do no preserve the raised stack (y,z,t). The HP-25c and HP-34c don't not preserve the display.


What about the new HP 10bii+?

All's preserved in the 10bii+ from what I can tell in my use of it.

Regarding the 20s, that explains why I lose display data. Glad that was brought up.


That is correct.

Basically, on the 10bII+ and 20/30b the calculator shuts itself off immediately after executing your keystroke. The display is left on, but everything else is shut down if possible. Essentially, unless it is saved in the "snapshot" of the system, it is lost immediately.


Edited: 31 May 2011, 4:27 p.m.


I've got a 20B that periodically loses all memory. Not just the display, but everything: data, modes, etc. Sometimes it'll happen after just a day of sitting on the shelf, sometimes it'll keep for a week or so. The 30B sitting next to it hasn't had the problem. Any ideas?

The 20B was one of the handouts at HHC 2010, if that means anything.


Your 20b has a super old firmware that was on the first batch of units ever built. That bug was fixed in the next back that was shipped less than a month later. If you have a cable, you can flash with the latest and you'll never see it again. Gene Wright can send either cable/firmare to you if needed.


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