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Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)

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Dave Wise:
<pedantic> EPROM, not EEPROM.</p>  The latter wasn't really a thing yet, and anyway is small capacity.

In some of today's computers, BIOS reads a few GPIO lines to identify the board.  The lines are grounded or pulled to Vcc according to board-unique manufacturing "stuff options".  Evidently Fluke did this too, with a bit somewhere in the chassis or front panel to distinguish between models.  Dust off your MDS-80 and trace the power-up code as it executes.

Dave Wise
Hardware/Software Engineer
Tektronix, Information Display, 1980-1994
Phoenix Technologies, 1996-2022

bdunham7:
Here are the front panel logic sections that would be involved.  Can you spot the difference(s)?  I haven't yet...

SilverSolder:

--- Quote from: bdunham7 on December 18, 2022, 08:02:57 pm ---Here are the front panel logic sections that would be involved.  Can you spot the difference(s)?  I haven't yet...

--- End quote ---


They are identical (I overlaid them in Photoshop).

bdunham7:
Well then, how does it know the difference?  I suppose there could be something elsewhere, like in the switch scanning circuitry.  The 8506A is a bit of an afterthought kludge in some ways, so I assume they just put something in somewhere for the code to look at in this specific instance.  That's why the controller IDed as 5.0.3 in an entirely wrong unit--that's the default and it only goes to 6.0.4 if it sees that 'something' that we don't know about.

Edit:  Well, the front panel diagram in my 8506A manual is labeled 8505A and appears to only have the switch/light labels for that.  The one in my 8505A manual actually has a flag and some alternate diagrams for the 8506A, but is missing a large part of the front panel switch section.    |O

m k:
Heh,
SilverSolder educated me once.

tip,
don't be narrow minded.

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