The Museum of HP Calculators

HP Forum Archive 15

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HP 9831
Message #1 Posted by Gordon Dyer on 1 July 2005, 6:21 p.m.

There is only a passing reference to this mdel in the MoHPC. Here are some pics:
http://www.decodesystems.com/hp9831.html

      
Re: HP 9831
Message #2 Posted by Tony Duell on 2 July 2005, 6:06 a.m.,
in response to message #1 by Gordon Dyer

What do you want to know about it (I have one)?. The hardware is the same as an early 9825 (with the system ROM module that slides in the right hand side under the keyboard). But those ROMs contain BASIC not HPL. And the keyboard has a few different keytops (it's the same arrangement of switches, same electrical matrix connections).

            
Re: HP 9831
Message #3 Posted by Eric Smith on 2 July 2005, 1:46 p.m.,
in response to message #2 by Tony Duell

So will the 9831A system ROM cartridge work in a 9825A, or vice versa?

                  
Re: HP 9831
Message #4 Posted by Tony Duell on 3 July 2005, 6:26 a.m.,
in response to message #3 by Eric Smith

I believe it will. I've been told that that's what people at HP did -- they had one machine on their desk and slotted in the appropriate system ROMs.

I belive you have the HPCC schematics CD-ROM. If you look at the 9825 keyboard schematics, it lists the (few) keys that were different. It also shows the 9831 (and not 9825) ROM module schematic, as that's what I have...

                        
Re: HP 9831
Message #5 Posted by Achim on 6 July 2005, 11:39 a.m.,
in response to message #4 by Tony Duell

What about making EPROM copies of the 9831? It would be extremly interesting for all 9825 owners.

                              
Re: HP 9831
Message #6 Posted by Tony Duell on 7 July 2005, 6:18 a.m.,
in response to message #5 by Achim

Remember the ROM chips in these machines contain the address decoder and address latch circuits (it's a multiplexed address and data bus). You couldn't just replace them with EPROMs, and you can't read out the HP chips in a normal EPROM programmer.

It probably wouldn't be too complicated to make an interface to normal EPROMs, and, indeed, reading out these ROMs is on my to-do list...

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