HP-41 Extended memory

Hi everybody:

Just wondering if anybody knows how to check the extended memory installed. I mean how to look at the registers that the calculators has in the extended memory (in order to verify that the modules work 100%)

Thanks in advance



Try doing a Catalog 4 (shift Enter 4). That should return how much extended memory you have installed. On the base 41CX with the extended function/memory built in, you should have 124 registers. Each extended memory module will have 238 registers up to a maximum of 600 with 2 extended memory modules. I think the extended function/memory module for the 41C/CV has 127 registers and you can add 2 extended memory modules to that for a total of 603.


If you have an HP-41C/CV as opposed to an HP-41CX, you will need to used the EMDIR command rather than CAT 4. CAT 4, CAT 5 and CAT 6 are only available on the CX.

On a C/CV with the X Function module alone or a CX with no X Memory modules, EMDIR will return 124 registers. Adding one X Memory module will return 362 registers and adding two X Memory modules will return 600 registers.

Mark Hardman

Houston, TX

Edited: 19 Mar 2004, 8:43 p.m.


Hi Jon, check your e-mail




I have an early 41C, and executing EMDIR results in a "NONEXISTENT" message. Is there some other way to check the memory on a 41c?


Take care.



I have an early 41C, and executing EMDIR results in a "NONEXISTENT" message. Is there some other way to check the memory on a 41c?

The HP-41C and HP-41CV do not have any extended memory unless you have plugged in an HP 82180A Extended Function Module, in which case they have 128 registers of extended memory. One or two HP 82181A Extended Memory Modules may then be added, which each increase the extended memory by 239 registers. (These counts do not match the output from EMDIR because some registers are consumed by overhead.)

The HP-41CV has 320 registers of standard memory, which is the maximum.

The HP-41C has 64 registers of standard memory. It can be expanded to a maximum of 320 registers of standard memory by adding up to four HP 82106A memory modules (64 registers each) or one HP 82170A quad memory module (256 registers).

If you're asking for a way to test the memory, the easiest way would be to write a small program to test it. For instance:

02 DEG
03 FIX 0
04 0.999
05 LBL 01
07 INT
08 360
09 /
10 SIN
11 SF 25
13 FC?C 25
14 GTO 02
15 RDN
16 ISG X
17 GTO 01
18 LBL 02
19 RDN
20 INT
21 "STO OK: "
24 1
25 -
26 1E3
27 /
28 LBL 03
30 INT
31 360
32 /
33 SIN
34 SF 25
36 FC?C 25
37 GTO 05
38 x/=y?
39 GTO 04
40 RDN
41 RDN
42 ISG X
43 GTO 03
44 INT
45 "RCL OK: "
48 LBL 04
49 RDN
50 LBL 05
51 INT
52 "RCL ERR: "
55 END

Use "SIZE" to set the number of registers to the maximum you can after entering this program. If the memory is initially empty, you can use "SIZE 044" on an HP-41C with no memory modules, or "SIZE 300" on an HP-41CV or HP-41CX. Then use "XEQ MEMTEST" to run the program. It will store a unique number in each register, display the count of registers it stored into, then recall and verify each number. It will take a while.


Thanks. I'll give the program a try.

I neglected to mention in my first posting that my 41c has two HP 82106A memory modules. They appear to be functional since the sum of the number of storage registers allocated and programming registers remaining (when no programs are stored) is 191. I was just curious as to why EMDIR does not work on my calculator, and was looking for a way to check memory when programs are stored without having to manually count bytes for each individual program.

I should also note that this 41C is a new acquisition and is my first experience with the 41 series. So, there may be an easy work-around which I have not yet stumbled upon or learned from the experts on this forum.

Take care.



The HP 82106A modules are not extended memory modules. They provide additional conventional memory for a 41C. The 41CV and 41CX cannot use the 82106A modules because they already have the maximum conventional memory installed. However, you can add extended memory to any of them with the 82181A modules. The 41CX has built-in software support for extended memory, but the 41C and 41CV do not. So, if you want to use extended memory in a 41C or 41CV you need the 82180A Extended Functions module, which has 128 registers of extended memory plus the additional software functions (like EMDIR) that support extended memory. The maximum memory configurations for each model are:

41C: One 82170A Quad memory module (the equivalent of four 82106A conventional memory modules, but only takes up one expansion port) plus one 82180A Extended Functions module plus two 82181A extended memory modules.

41CV: One 82180A Extended Functions module plus two 82181A extended memory modules.

41CX: Two 82181A extended memory modules.

These configurations result in the same amount of memory for all three models, but the 41C will have all four expansion ports filled, the 41CV will have three ports filled, and the 41CX will have only two ports filled.

You can think of a 41CV as a 41C with four 82106A modules (or one 82170A quad module) built in, and a 41CX as a 41CV with an 82182A Time Module and an 82180A Extended Functions module built in. (The 41CX also has a few additional built-in functions not included in the other modules.)


Thanks for the education, Wayne. That's the clearest explanation I have gotten as to how the memory works among the 41c models.

Take care.


PS - You don't have a spare Quad Memory module you want to sell, do you?


Do I have to "max out" my conventional memory on the 41C before I can use extended memory module(s), or can I install an extended memory module and/or the Extended Functions module and take advantage of extended memory with just "base" conventional memory?

Thanks again.



You can use an Extended Function module, which includes 128 registers of extended memory (slightly less usable due to overhead), without having the full complement of conventional memory.

On an HP-41C or HP-41CV, you can't take advantage of Extended Memory modules without having the Extended Function module.

The HP-41CX has the equivalent of the Extended Function module built in, so you should not put one in a port. But you can use the Extended Memory modules in an HP-41CX.

You can have at most two Extended Memory modules. They must not be installed one above the other. They can be side by side, or diagonal from each other.


Thank you, Eric.

You and Wayne have been very helpful in getting me up to speed on the 41C. I really like the one I just picked up. It is apparently a pretty early one (Ser.# 1942A00288), and is the "steep key" model. I just started messing around with programming it this past weekend. It's fun.

I am already shopping for another one; hopefully a later model CV or CX.

Thanks again.

Take care.



Hi Wayne ("don't give your pelt to the trapper") Brown,

Yes, I agree with Wayne Stephens--yours is an excellent uderstandable description---thanks!

Bill Platt


The today configuration is a HP41CX (with internal X-Functions + Time-Module), a Double X-Memory / XX-Memory (two X-Memories housed in one module case) and the CLONIX.

Load the CLONIX with rom images like CCD + EXT-I/O + EXT-IL and you get an really advanced handheld computer configuration.

Add the IL-Module, the HP-IL/PC Interface Card and EMU41 and you have a absolutely great system solution....

Regards from Germany - Christoph Klug


PS - You don't have a spare Quad Memory module you want to sell, do you?

No, I'm afraid the only memory modules I have are Extended Memory and they're both in use in my 41CX.


You obviously recognize me from comp.sys.hp48. :-)

You're welcome. I've gotten lots of useful information from people here, so on those rare occasions when I have something to contribute, I like to share (sometimes at great length!). :-)

Possibly Related Threads...
Thread Author Replies Views Last Post
  HP-41(CL): The easiest way to transfer FOCAL programs from a Linux PC to the HP-41 Geir Isene 13 2,449 12-05-2013, 02:40 AM
Last Post: Hans Brueggemann
  ILPer with "auto-extended addressing" Christoph Giesselink 0 481 07-23-2013, 03:28 PM
Last Post: Christoph Giesselink
  41 User Memory vs System Memory Gerry Schultz 6 1,016 07-01-2012, 12:02 AM
Last Post: Monte Dalrymple
  HP-41 Memory chips info (for those HW guys out there :-) Diego Diaz 3 695 03-24-2012, 08:06 PM
Last Post: Diego Diaz
  DM-15CC Extended Memory Mark Hardman 4 725 02-17-2012, 12:18 AM
Last Post: Paul Dale
  [WP34s] Questions about extended precision fhub 7 926 10-28-2011, 05:20 PM
Last Post: Marcus von Cube, Germany
  HP 15c LE - Extended PSE Functionality? Alexander Oestert 18 1,964 09-30-2011, 11:13 AM
Last Post: Alexander Oestert
  HP-41 strange Memory Module found. Diego Diaz 0 346 08-20-2011, 10:18 AM
Last Post: Diego Diaz
  HP 41 key assignment file and x memory Geoff Quickfall 13 1,337 08-15-2011, 01:00 PM
Last Post: M. Joury
  Extended TVM-solver for the WP34s fhub 28 2,909 08-09-2011, 05:55 PM
Last Post: fhub

Forum Jump: