HP-71B: 82490A or 82441A

[Joe Horn]

(08-26-2015 01:29 PM)smp Wrote:  One of my hobby things is to get the Forth language working on each of my vintage computers. I understand this is achievable with the HP-71B: one needs to acquire the 82441A Forth/Assembler ROM. ...

I also understand that there is another route: acquire the 82490A 41CV Translator ROM. ...

I understand that the 82441A ROM is available in order to specifically make the HP version of the Forth language available, but I also understand that the HP version of Forth is also fully available in the 82490A ROM.

My question to the group is this: If I were to drop an outrageous sum of money to acquire one of these ROMs, which one should I choose? My desire is only to be able to use the HP version of the Forth language. I really do not intend to use the assembler in the 82441A ROM or the 41CV translator in the 82490A ROM.

Is one of these obviously "better" that the other? Is the 82490A ROM more limited in any way? Do both ROMs have the same capabilities?

The following quote from page 74 of the HP-41 Translator ROM might be helpful:

Quote:Relation to the HP-71 FORTH/Assembler ROM

The FORTH system contained in the HP-41 Translator Pac is very similar to that in the HP 82441A FORTH/Assembler ROM. The HP-41 Translator Pac does not contain an assembler, but its built-in word set contains additional floating-point words and other HP-41 words not found in the FORTH/Assembler ROM.

The floating point words in the HP-41 Translator Pac differ from their FORTH/Assembler ROM counterparts in two respects:

• The HP-41 Translator Pac words will error if any of their arguments are alpha data.

• The HP-41 Translator Pac words perform a stack lift only after computation is finished, so that the stack is unaffected if a word terminates due to an error. In the FORTH/Assembler ROM, the stack lift is performed before the computation.

FORTH words defined from words common to both modules can be compiled into either system from a text file containing the definitions. However, because the addresses of built-in words and user variables are not the same in the two systems, you should not attempt to exchange files of type FORTH between the systems. That is, a file originally created as FORTHRAM by the FORTH/Assembler module should not be renamed as FTH41RAM for use with the HP-41 Translator Pac, and vice-versa. The most likely result of such an exchange is the Memory Lost error.

Bottom line: If all you want to do is play with Forth on the '71, and not assemble Saturn code nor use the HP-41 translator's unique features, then I'd suggest getting whichever is cheaper, since their Forths are almost identical.

By the way, you can freely download both as ROM images (they are both on this LIF-disk image), and install either one in a IRAM, if you own a PIL-Box, and if you can FREE a big enough IRAM to hold the ROM image.