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Which calculators run RPL under the hood?
12-09-2019, 06:48 AM
Post: #20
RE: Which calculators run RPL under the hood?

Down through memory lane we go...

- The double execution prolog thing was kind of a genius idea, I still remember when I discovered it/understood it myself. it was a woha moment...
- Rpl is great as it allows manipulation of "objects"... But it still lakes some stuff, like the ability to define new object types, which is sad...
- Rpl is definitely WAY better than ASM when you have to develop things as it is much less error prone, less likely to cause crashes...
- The main issue in my opinion is that the Saturn chip is NOT at all adapted to RPL. RPL, with its constant object creation/destruction is very memory intensive... But the Saturn chip is NOT good at memory movements, which is problematic and the cause of a lot of slow downs in the Rpl machines... However, I venture to guess that at the time, speed was not a big issue as UI was, at least initially very under developed. it did not become an issue until the 48 came along...
This is especially true as, at this point, most of the team seemed to only write RPL and did not seem to think about dropping to ASM for critical items. See the equation writter for example, which was nearly unuseable :-(

Anyhow, they did indeed reuse a lot. Here is the header from the basic math source code from the 38/39/40/48/49/50 series (it is the same file)... as you can see from the date, it is not a youngling!

TITLE Saturn Basic Math Routines 1.1
** File: math0.a Version 1.1, 10/26/87
** Machine: Charlemagne
** Covered by GG 12-28-88
** UnCovered by GG 01-06-89

Apart from the 38/48 series calculators, none of the ACO and later calculators are RPL based (starting with the newer 10BII, 17Bs, 32SII, 35...)
They are all developed in C, using a math library which is a "copy" in C of the math library used in the 95LX, which is itself a copy in Intel ASM of the saturn one...
Unfortunately, it is a a rather simplistic implementation, based, somewhat on a virtual implementation of the Saturn CPU. So it is slow as hell...
In 2004 or so, when it became clear that we would be working more and more with ARM chips for low end calcs, I recreated the whole math library in C, but as a recreation based on the code rather than a copy. This library is what is used in Prime and a couple of other calcs...



Although I work for the HP calculator group, the views and opinions I post here are my own. I do not speak for HP.
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RE: Which calculators run RPL under the hood? - cyrille de brébisson - 12-09-2019 06:48 AM

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