hp41cv memory modules


What is the difference between modules hp82106 and hp82181? I already have "x-functions" hp82180. Do I gain anything by using both hp82106 and ho82181? I"M aware that I won't get anything from using a quad memory module.


An 82106 is for use with a 41C only. That functionality is already built into a 41CV or 41CX.


The 82106 is a 64-register RAM module, intended to add more registers to a 41C. The 41CV and 41CX already have the full complement of memory registers, so you don't want an 82106 for one of those.

The 82181 is 238 registers of extended memory, intended for use with the 82180 x-functions module (which itself contains 127 registers). With the max of two 82181's, you can extend a 41CV or CX to 603 registers of extended memory.


--- Les



The original 41C (C, not CV or CX) came with 448 bytes of RAM (yes, minus three permamently occupied bytes). It could be upgraded to a maximum of 2240 bytes. There were various RAM-modules: Up to four 82106A modules with 448 bytes each could be added, or two Double-RAM modules with 896 bytes, or one Quad-RAM 82170A with 1792 bytes.

All these RAM modules can not be used on a 41CV or 41CX, as these machines already have the maximum amount of memory built in. They come with 2240 factory-installed bytes. So there is no use for any of these modules in a 41CV or 41CX.

Extended memory ("X-memory") is a different story. It is added to the conventional RAM and the user may transfer data between regular RAM and X-memory. You may think of it as a kind of RAM-Drive (well, sort of). To use X-Memory, you plug in a 82180A X-Functions/X-Memory module. This module adds a set of handy additional functions (hence the name X-functions), and it also provides the required commands to deal with X-memory. A certain amount of X-memory already is built into the module. Further X-memory modules 82181A can be added to expand X-memory. So the 82180A is always required, and one or more 82181A modules are optional.

This means you can neither use the 82180A (not required and not useable with the 41CV) nor the 82181A (requires a 82180A X-functions/X-memory module).


Edited: 6 Nov 2013, 4:15 p.m.


I just got a hp-41cx (my very first foray into hp-41 land) and have been trying to get clear on this very topic.

I would like to make sure that I understand this correctly:

The 41CX already has the X-functions necessary to access X-memory built into it. So, you do not need to have a X-functions module. However, unlike the X-functions module, it does not have any X-memory built into it. So, on the 41CX, if you actually want to use the x-functions for accessing the X-memory you do have to add an x-memory module.

Are the X-memory modules static RAM or do they get wiped when they are removed from the calculator?


A cx already have 128 extended regs built-in. You can still use 2 82181A X-memory modules to have the max capacity.

Edited: 6 Nov 2013, 5:47 p.m.


Thanks. I am glad I asked - I was not clear on that.


All of HP'S RAM modules for the 41 family are static RAM, but they are volatile and will lose their contents pretty quickly after removal from the calculator. Sometimes people have succeeded in transferring data from one calc to another by quickly swapping modules. Some people even added capacitors to the modules to facilitate that.

The trickier problem is ensuring that the memory map on both calculators are aligned to be conducive to such a swap. That's not too hard for the top-numbered 64 or 256 data registers, but much trickier for program memory and extended memory.

Edited: 6 Nov 2013, 7:45 p.m.


Does keeping the extra memory in the calculator shorten the shelf life of the batteries in any significant way?

When changing batteries, do you risk losing memory, or does the memory not lose its contents that quickly?



the only memory that i loose when changing batteries is the time in a cx. i've even saved that if i have a good battery holder to switch out real fast.


When I got my double extended memory module for my 41cx, the battery life dropped from maybe two years to around six months, but I suppose it's just that one of the two modules built into the one package is kind of leaky. I suspect they didn't all do this. It works fine though, and I filled up the XMEM space without taking more than one port space. I also have the XIO built into the HPIL module, so I can effectively have six modules plugged in at once.

I don't lose anything at all when I change the batteries-- not even the time. I'm very quick about it though, so I don't know if that has something to do with it.

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