TDS 512MB cards and HP48SX

[JoJo1973]

Hi everybody,

I've researched for a multi bank expansion card for my old faithful 48SX, but all I've found are GX cards.

I remember having read that many cards labeled for GX can be used on the SX provided a bank switching library is installed. I've also read that some cards are NOT hardware compatible, but not being an expert in this field this information might be not exact.

Could anyone confirm this? In particular I'm interested in a 512MB card from TDS. It's the green one, labeled for GX. The owner has no documentation for it but has provided me with the serial number, in case it might be useful for identification.

Does anyone know also if it is compatible with the bank switching library on hpcalc.org?

Thanks!

[Raymond Del Tondo]

(05-26-2016 07:55 AM)JoJo1973 Wrote:  I've researched for a multi bank expansion card for my old faithful 48SX, but all I've found are GX cards.

The GX cards only make sense in a GX. The HP 48GX uses a special access mechanism, which only the GX compatible cards implement.

There may not be many TDS MultiMemory cards for the SX available, since the older ones from 1990-92 had a hardware bug which rendered them unusable on certain battery level conditions.

(05-26-2016 07:55 AM)JoJo1973 Wrote:  In particular I'm interested in a 512MB card from TDS. It's the green one, labeled for GX.

Then you'll only be able to access 128K of the card in the SX, and it may even not be guaranteed to get the same 128K page after the next startup.

(05-26-2016 07:55 AM)JoJo1973 Wrote:  Does anyone know also if it is compatible with the bank switching library on hpcalc.org?

No, the TDS switching library only works with the older TDS MultiMemory cards made especially for the SX.

However there exists a version of the TDS switcher which works on the GX, so if you put an older TDS MultiMemory card for the SX into port 1 of a GX, and install the GX version of the switcher library in port 0, then it should work.

The were some related forum discussions in the past.

You could also consider getting a GX, which would simplify several things;-)

[JoJo1973]

Oh, what a shame... I just wanted to add some punch to my old 48SX. For more serious number crunching I already have a 50G.

Well, never mind, and thanks for the info.. Anyway it's interesting to know that old SX card are subject to this nasty hw bug... do you remember the cause?

Regards,
Stefano

[Raymond Del Tondo]

(05-27-2016 05:41 PM)JoJo1973 Wrote:  Anyway it's interesting to know that old SX card are subject to this nasty hw bug... do you remember the cause?

The old TDS MultiMemory cards for the SX were somewhat sensible in certain situations, e.g. when the card's battery was low.
In those cases they tended to short-circuit, which led to the obligation to replace a small chip on the card.

[mfleming]

Raymond,

Could you identify the chip and replacement procedure for the card problem you mentioned? I pulled my old 48SX and TDS memory card from storage a few months ago, and the card stopped working shortly after turning the calculator on. I've never seen a reference to this hardware fault, so I'd like to investigate further.

Thanks!
~ Mark