Max ram on a 71B

[Steve (Australia)]

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 :-)

[Peter Petersson (Germany)]

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.

[Steve (Australia)]

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.

[Peter Petersson (Germany)]

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

[Steve (Australia)]

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 :-)

[Reinhard Hawel]

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.

[Chris Catotti]

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.

[Reinhard Hawel]

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.