Re: 9825T ROM failure Message #6 Posted by Alex on 23 Aug 2004, 5:08 p.m., in response to message #5 by marais
I don't think that ROM dumps exist for most of the 9800 series desktop machines because HP didn't usually use industry standard ROM devices. In many cases HP was "ahead of the curve" and developed their own ROM technology. I've seen this in both HP Journal articles and by talking to people who used to work at HP. In some of them, the ROM chips do more than just the ROM function, they have address latching and/or decoding. In other cases, it may be possible to make a pinout adapter for an industry-standard ROM to fit in the spot of a bad one. I have a 9830A with a bad ROM and would sure like to fix it, and it would also be great to be able to get the Option ROMs copied for the earlier machines, but I haven't found anybody who has successfully done those things (so far). Without schematics for the 9800 series (which don't seem to exist), it would be difficult to reverse-engineer (although Tony D. may be able to help out here, Tony ????? ).
An exception is the HP85 series, while the ROMs themselves are special, there is the "Programmable ROM Drawer" device available that uses 2764 devices (with a bunch of external circuitry to emulate the address latching/decoding/etc. inside the ROM chip), and Vassilis Prevelakis has a bunch of the ROM images on his great website.
Alex K.
The Calculator Museum Web Page
http://www.calcmuseum.com
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