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'91 TDS 256KB RAM Card for the HP-48 SX
03-21-2015, 06:06 PM
Post: #8
RE: '91 TDS 256KB RAM Card for the HP-48 SX
(03-19-2015 11:39 PM)Christoph Giesselink Wrote:  
(03-19-2015 08:16 PM)Guenter Schink Wrote:  I can't tell of course. But the discussion here sounds like it is possible?

Just got a report, these cards really exist for the SX and it seem that the bank switching was activated by a special read sequence. This version of Super Switch can definitely handle cards for the GX. I had a short look inside the decompiled source code and found a code sequence typically for accessing a memory card inside slot 2 of a GX (conditional UNCFG the module at address #C0000, normally a card in slot 1, to get access to the covered memory below, in our case to the card in slot 2). This code sequence makes no sense on a SX, because there's no covered memory at #C0000.


If you look a further down in the disassembly of the directory, it says that it's for the HP48GX. Or just open the DOC804 variable :-)

I have always wondered if these cards had extra hardware to handle the bank switching since the HP48SX itself doesn't have any bank switching mechanism built into its hardware. I have never owned such a card, nor would I open one up if I did just to see.

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RE: '91 TDS 256KB RAM Card for the HP-48 SX - Han - 03-21-2015 06:06 PM

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