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Comment by iforgotpassword | Hacker News Reader

This is awesome:

> The HP 49 series initially used the Saturn CPU as well, until the NEC fab could no longer manufacture the processor for technical reasons in 2003. Therefore, starting with the HP 49g+ model in 2003, the calculators switched to a Samsung S3C2410 processor with an ARM920T core (part of the ARMv4T architecture) which ran an emulator of the Saturn hardware in software.

Surprising, but also pragmatic, but then again is that really cheaper than porting a calculator os to a modern CPU?

> The HP 50g, the last calculator utilizing this emulator, was discontinued in 2015 when Samsung stopped producing the ARM processor on which it was based.

I have an idea how to solve this... :-)

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This family of calculators was built around RPN, a Forth inspired language.

The thing is that language tokens were not exactly interpreted in the classical way, they were converted to address of routines in the 512K ROM (or RAM for more dynamic objects)

Programming language, OS and hardware were very closely coupled.

RPN was invented in 1924, Forth in 1970.

https://en.wikipedia.org/wiki/RPL_(programming_language)

The RPN notation, yes.

But the language used the Saturn based family of calculator is using this notation but also many concepts inspired by Forth.

> is that really cheaper than porting a calculator os to a modern CPU?

There was a whole OS and programming environment in there, very closely tied to the CPU architecture. All the calculator's advanced functionality, including graphing, equation editor UI, equation solver, compiler and decompiler, etc., was written in the OS's own stack-based system language. Porting all of that to another CPU family would definitely have been much more work than writing an emulator for the old Saturn CPU. Performance must not have been a problem, thanks to ARM and Moore's law.

Quite different, by try "porting" NES games to a modern CPU, for example using zero page instead of just doing operations between registers that more modern CPUs allow unlike the 6502. Different programs from different times were made with different assumptions. It's much easier to emulate (and they games will actually run correctly).

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