Joe's HP 9831 Computer

Revised 10/19/2000

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The 9825, 9835 and 9845 Series (including the HP 9831).

Unlike the 9810, 9820 and 9830 series, the 9825, 9831, 9835 and 9845 were not all released at the same time. Also unlike the earlier series, the 98x5 series including the 9831 shared many common interfaces and peripherals.

HP 9831, Neither Fish nor Fowl!

The HP 9831 is a strange machine, it looks like a 9825 but runs 9830 BASIC. It's a cross between a HP 9830 and HP 9825 but I consider it to be part of the 98x5 series since it was based on a 9825 and used the same interfaces as the 98x5 machines. It was only listed in the 1978 HP catalog and was listed as a new model that year. The description says that it runs BASIC and has 7162 bytes standard but is expandable to 32k. The 9831 had the Matrix, String Variables and possibly some of the HP 9830 ROMs built-in. I asked HP about the 9831 and here is what they had to say. "The 9831 used the 9825's hardware and the firmware was a rewrite of the original 9830 code. Many 9830 lovers wanted to be able to program in HP Basic but use the new, much faster hardware and the superior tape storage. I don't think this project required much more than pulling out the 9825 system ROMs (picture) and plugging in the 9831 ROMs. In fact, as I recall, some of us kept two system-ROM drawers around so we could change the machine's personality at will." This seems to be a VERY rare machine. I only know of three examples that exist. Other than that one appearance in the 1978 catalog, I have never seen it mentioned in any of the HP catalogs or literature. The HP 9835A and B were both released the next year and both used BASIC so apparently the HP 9831 was quickly dropped. The 9831 uses the standard HP 98x5 interfaces and peripherals.


(1978) = $ ???

9831 Options and ROMs

AFIK there were no options or ROMs for the 9831, it had everything possible built in.

Size and Weight:

Base 15 x 21 x 5 inches 26 pounds

Click here for a list of HP 9831 interfaces.

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