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HP 86: Strange Error
11-19-2017, 04:23 AM
Post: #3
RE: HP 86: Strange Error
(11-19-2017 12:22 AM)rprosperi Wrote:  
(11-19-2017 12:07 AM)Michael Fehlhammer Wrote:  My newly acquired HP 86A displays a strange warning immediately after power on:
Warning 27: 85 ROM disabled.

Michael - The HP-87 "Operating and BASIC Programming Manual" (I don't have '86 docs, but as you know they are quite similar) includes Error 27 (a warning) in the Error Message Appendix with this Error Condition note:

"An HP-83/85 ROM is installed in the ROM drawer. The ROM is ignored by the system if no ROM with the same ROM number is present."

The wording of the final sentence is a bit strange to me, as I'm not sure how some other ROM could have the same ROM number as an 83/85 system ROM; perhaps this could happen if some signal lines on a board are damaged?

Any chance there are additional ROMs installed internally?

Assuming it's a false positive, I'd say it's likely safe to ignore as far as how it will affect your use of the machine, since it is disabled. The actual cause of the condition may be reason for concern though as something is being detected incorrectly.

The "ROM number" it is referring to is the select number the ROM is programmed to respond to. In the series 80 machines ROMs are selected by writing this ROM number to a specific address that all the bank selectable ROMs monitor and when a ROM sees its number come up, it enables itself, and if it is someone else's number the ROM disables. Between the 83/85 and 86/87 machines ROMs with similar function have the same ROM number, for instance the assembler ROM is ROM number 40 on both, and if you had both the 83/85 and 86/87 ROM plugged in at the same time both would respond to the ROM number by turning themselves on and the result would be unpredictable, I would suppose that a defective ROM could cause a similar result, the best way to check would be with a diagnostic ROM as it does a more comprehensive test of the ROMs .
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Messages In This Thread
HP 86: Strange Error - Michael Fehlhammer - 11-19-2017, 12:07 AM
RE: HP 86: Strange Error - rprosperi - 11-19-2017, 12:22 AM
RE: HP 86: Strange Error - Paul Berger (Canada) - 11-19-2017 04:23 AM
RE: HP 86: Strange Error - Martin Hepperle - 11-21-2017, 01:48 PM



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