The never-released HP-72S / HP-74S - the successors of the HP-71B

[Sylvain Cote]

(04-09-2021 02:57 PM)rprosperi Wrote:  Thanks for the fixes J-F!

... and thank you Robert for all the beta testing that you have done.

[J-F Garnier]

(04-09-2021 02:57 PM)rprosperi Wrote:  I've installed lots of ROMs, and > 30 LEX files and have encountered no compatibility issues to date, using the v0.91 version.

This was the most important request from the marketing dept: make the 72S fully compatible with the 71B

Quote:Note: Some programs (e.g. C71) use the WINDOW command to control output and may leave such settings in place, which can appear to have disabled the wrapping feature when using the 2-line display in Emu72. If this happens, just use the command 'WINDOW 1' to reset its defaults and the wrapping display will be restored.

There are some interesting things you can do with the WINDOW command on the 72S:
- with WINDOW 1,22 you are in true 71B compatibility mode,
- you can also do WINDOW 23 to use only the lower line. This is how I made the illustration picture above (and on my site):
VER$ @ WINDOW 23
- you can also use funny settings such as WINDOW 12,33...

J-F

[Dave Frederickson]

(04-09-2021 04:41 PM)J-F Garnier Wrote:  There are some interesting things you can do with the WINDOW command on the 72S:
- with WINDOW 1,22 you are in true 71B compatibility mode,

I presume this would be the desired mode when loading 3eeee firmware into FRAM71?
Modify your JPC ROM ML file accordingly.

[Alejandro Paz(Germany)]

Very nice work ! I see that my dream of a 4 or 8 line 71 may not be that crazy !

But I have a question regarding these routines to extend the stack: RSTK<R and R<RSTK, they extend the stack lets say from 8 to 24, adding up to 16 levels. Do you see any benefit from implementing a deeper stack and avoiding these routines ? (one would have to skip over these long gosubs/very long gosubs (4 levels needs ~63 opcodes).

[J-F Garnier]

(05-27-2021 01:55 PM)Alejandro Paz(Germany) Wrote:  But I have a question regarding these routines to extend the stack: RSTK<R and R<RSTK, they extend the stack lets say from 8 to 24, adding up to 16 levels. Do you see any benefit from implementing a deeper stack and avoiding these routines ? (one would have to skip over these long gosubs/very long gosubs (4 levels needs ~63 opcodes).

Yes, the Saturn hardware stack is very limited: 8 levels, one of them used for interrupts. The HP71 OS had to save levels with these RSTK<R and R<RSTK routines, still stack overflow (i.e. lost of a return address) was the cause of several bugs of the 1BBBB and HPIL:1A versions in special conditions. In many places there was few or no spare levels and it was difficult to check all the special cases and paths (error, exception, ...).

Still now when developing new LEX, ensuring no stack level lost is a major concern. For instance, functions can only use 4 return levels, and it's easy to reach this limit when calling system routines, thus requiring to save levels at the right points.

So yes, having a deeper hardware stack would be very welcome.
Actually, Emu71/DOS already emulates a 64-level stack, although it is not used at the moment, it ensures that "Memory Lost" conditions due to stack overflow will no more occur.
Emu71/DOS also implements the R5-R7 registers, that are not existing in the real Saturn but that are allowed by the opcode coding structure.
The hypothetical Titan X enhanced CPU would have implement these improvements, and other ...

Ultimately, this could allow us (me?) to build the 72S/74S ROM with these enhancements.

J-F

[sa-penguin]

If there was an "in line" USB module, that had an LCD...
And sat between a standard keyboard and a PC...
And could be invoked using a "Hot" key combination...
...that could be used as a calculator.

Don't even need a PC, either - a USB power supply would be enough.

Of course, someone would put a 2nd USB port on it, throw a memory stick on it, and use it to edit files. Or encrypt / decrypt data without exposing the key to the PC.

People can be very inventive.