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Just for the fun of it I inserted 1x128K and 4x32K modules into a 71B and it now reports 279040 bytes of RAM.

I was under the impression previously that with the 128K module inserted that you couldn't add further RAM.

Obviously I was wrong.

How much memory can this device handle?

I note that the address space is 512kB.

Oh, and it seems to take longer to turn on now too :-)

Hi Steve,

You can add one more RAM module in the IL slot, it
has the same connector than the front slots, and can
be used for additional RAM.

MEM now reports 311781 bytes!

Did HP71b's ever get made without HPIL interfaces?

If so, then I suppose I could find a blank plate that might cover the IL port with the 32K memmodule inside.

Otherwise it's really just an interesting curiosity.

I remember my max. was 320k once (I manufactured some memory expansions together with two friends more than 10 years ago).

There's no limitation besides the 512 k address space (and the position of the I/O addresses). There are the lowest 96k reserved for the ROM and memory mapped I/O purposes (I believe), so there are 416 k rest. I'd guess, I'm one of the 10 people in the world, who have ever seen the message ERR:Configuration .

This message means, there are too much modules inserted to be configured into the 71Bs address space.

BTW: just try to fill up all this memory with LEX files. The 71 will get unusable slow. There's a lot of poll handlers to be checked for every event occuring in the 71s OS.

The 71B was sold without the IL interface, it was a $125
accessory! But I have no spare cover for You, sorry.

Amazing. You know, I've never seen an HP71b *without* an HPIL interface!

Probably because they seemed here to be used by Goverment for mobile data capture and storage and thus needed the tape drive and printer.

Looking around in a box of bits I came across a cover!

Since I had never seen an HP71 without one I had never twigged that they were even removable! And thus I had not considered that the funny cover might fit somewhere :-)

I believe EduCALC use to offer a service where they would hardwire RAM modules internaly in the HP-71, thus freeing up ports for ROM. If I recall, they could piggback or daisychain one to the next up to the maximum limit of ___?

If you are interested I could look through old catalogs, PPC Journals, or CHUU Journals until I remember what I think I read.

I believe they could hardwire 8 * 32k RAM into a HP-71B, so there was (in theory) place for an 128k card reader port module and 4 front port modules (together 128k).

These sum up to 512 kBytes and would surely cause an ERR:configuration together with the HP-IL module(16k), the I/O address space (32k ?) and the ROM (64k)

I have to search for my older EDUcalc catalogues.

I looked into my HP papers 5 seconds and found some younger catalogues (1991 and 1995).

There was no theoretical limit to the daisy-chaining method (yes, the plugin units were configured with software commands in the OS during startup code). An exception is the 48k Forth ROM (Assembler and Translator) where a 32k part was hard configured to #E0000 - #EFFFF. There was an additional 16k Soft configured part in the module.