An unusual HP 71B - questions


Hi folks,

I recently purchased another HP 71b in trying to complete my "perfect 71." However, this 71b was very unexpected and has some unusual characteristics. I don't know what it is; it's some sort of Franken71 and hopefully you can help me identify what's going on.


1. Why does my new 71B have 168,443 RAM and VER$ has "FTH:1A EDT:A KBD:B" when all 6 slots are empty?

2. Why can I add only 4K extra RAM with software modules or lots of RAM but no software modules?

(Now, I read but didn't entirely understand it. This might be the answer to #2.)

Long version:

With everything removed (all 6 ports including front) and batteries, the calculator reports the following:

MEM: 168,443

Now, as I recall, a stock 71b should be reporting about 16k of MEM and just the HP71:XXXXX in the version. So, I have one that strangely has over 160k of RAM and Forth. (It is because it had Forth I purchased it; I wanted a Forth module, but this is not a module!) I am not sure what KBD:B means. It passes the ROM self-test (ON-/, 2).

It also came with a module that looks blank but with a golden label with no writing. This module when inserted modifies calculator to:

VER$: (as above) WB:D TXTU:A

WB is the 71b spreadsheet. I'm not sure what the TXTU:A is. It also came with a CURVE FIT module. Adding that adds in a "FIT:A" to the VER$ response. Then, adding the HP-IL module that it came with adds "HPIL:1A" to the VER$. Those are expected.

Next, I add a 96k card reader RAM module to it, but the calculator now gives me an error: "WRN: Configuration" when I start it up. MEM now reports 266,697, but the VER$ now shows "HP71:1BBBB FTH:1A EDT:A KBD:B HPIL:1A WB:D TXTU: A" so the FIT:A is no longer being seen. Removing the 5061-7241 CURVE FIT still results in the 71b saying "WRN:Configuration."

Removing both modules, so that the only things installed are the 96k card reader RAM module and HP-IL module causes the warning to go away. MEM is still 266,734.

In the next test, I now add a 32k module (Front slot, Corvallis) and again now I get the WRN. Nonetheless, the RAM seems to be accepted, as MEM reports 296,546 and VER$ reports "HP71:1BBBB FTH:1A EDT:A KBD:B HPIL:1A". Adding another 32k module now shows 329,356 MEM, and VER$ shows only "HP71:1BBBB!" and continues with the warning. Adding 4k modules one at a time shows more memory each time, but now there's just RAM.

If I take out the 96k card reader RAM module, I can then put in all my other modules (HP-IL, Math, Curve Fit, and the strange WB/TXTU) without an error. VER$ reports HP71:1BBBB FTH:1A EDT:A KBD:B HPIL:1A MATH: 1A FIT:A WB:D TXTU:A" so it's all being seen, with MEM of 168,338. Adding a 32K module to the front will return the WRN:Config error, but the VER$ is the same as before and MEM is 201,106 as expected, so I'm not sure what's now the problem.

Replacing the 32K with a 4K reports MEM of 172,429 and no configuration problems!

Unfortunately, I have no more software modules to test, no card reader module to test (I'd love to get one), and I imagine the 64K RAM card reader module I have would do the same thing as the 96K module given the results with the 32K front port module.

So, what's this odd 71b I have? And what's with the "too much RAM" WRN problems?




I saw photos this calculator recently. :)

Through the mid 80's EDUCALC had an upgrade service whereby they combined HP41C roms and another where they added Modules inside HP71b calculators. I have one of these machines that has extra ram internally, and I have had others with FORTH or similar modules stripped of the casing and hard-wired in the box.

Out of a few dozen 71b's I've touched, probably 4 or 5 have had this kind of modification.

No advice on the other WRN messages. Congrats on a neat find.


Congrats on a neat find.
+1!! That is an enviable machine. Its 512KB of address space is nearly full, with a lot of RAM and other modules added interally.

Edited: 14 Jan 2013, 7:15 p.m.


That is weird! I have a prototype 71B that comes up with "TI%RM4-HP71:0AAAA" when you type VER$. See HERE

It has 16k of memory instead of the normal 32k. Cheers, Keith


16K was standard. I've never heard of one coming with 32.


Sorry I meant 8k instead of 16k. Now i'm not sure - i'll have to dig it out and confirm.


"TI%RM" is the name of one of the source code files for the 71B firmware. Possibly the 4 is a revision number of that file.


The total 71b address space is 512KB, but 96KB of that is taken up by the firmware and the I/O space. Since you have an extra 160KB of RAM and several ROMs preinstalled, your address space is nearly full, so you won't be able to use too many ROM modules or high-capacity RAM modules simultaneously.


Thanks for all the useful replies so far. I seem to have gotten lucky with this 71b and don't need much more to finish my ideal 71 now. Too bad this calculator can never use the 41 Translator because, as I recall, that's incompatible with the (now permanently built-in) Forth module.

On this page: I have identified the odd blank front module that has just a gold label. It looks to be a "Corvallis CMT71 EPROM" of either 32K or 64K size. It has the "WB:D TXTU:A" programs in it.

Does anyone know how to distinguish the two EPROMs apart (just to satisfy my curiosity), please? I read in other threads here not to mess with it or risk losing my programs.

Also, could anyone please tell me what these two programs are?




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