TDS-256k RAM Card


Do these work on a 48-GX?

I cannot initialize this on my GX and was wondering if that is the problem.


Built in battery or replaceable? My TDS had a built in battery which needed replacing.

check out this posting from a while ago to gain access for the built in battery:

Access to the TDS battery

Of course, format the card and etc before accessing the battery.

Cheers, Geoff


I've replaced the battery. It came to me with none. I run PINIT but I can't eliminate the message "bad card data".

Do I need the TDS softare to use this ram card?


Do I need the TDS softare to use this ram card?

No, I have used one in my 48GX without TDS software.
(Mine came with a TDS surveying card, the RAM card can be used without the surveying software, but the surveying software can't be used without a RAM card)

My 2c worth

Edit: on reading Geoff's post, a note: I had a 256K TDS RAM card specifically for the GX, thus not a bank switching type.

Edited: 5 Apr 2011, 6:17 p.m.


Someone may correct me but I just googled tds ram card hp48gx and came up with the following link:

256 and 512 TDS cards

I don't know if this is true but I pulled the following quote from the site:

6.24 I've heard about other manufacturer's RAM cards. Will they work?
While some cards may work, there is a chance that you may severely damage your HP48. You should only use cards specifically designed for the HP48. Naturally, HP sells such cards, and some third parties also make cards that will work in an HP48. Some cards work with both the S/SX and the G/GX. Some, however only work on the S/SX, or only on the G/GX. Make sure that the card is designed to work for your version before using it.

The S/SX can only naturally support up to 128K per port. HP sells 32K and 128K RAM cards. However, TDS, using software "bank switches" produces 256K and 512K RAM cards. These bank switching cards do not work in the G/GX series. CMT also makes 128K cards, which work in all HP48 calculators.

While you cannot use the TDS 256K and 512K cards, Sparcom has come out with 256K and 512K cards for the G/GX only. HP also sells 1MB RAM cards that work for G/GX only. The G/GX is able to accept a 4MB RAM card, but none are on the market at this time.

It may be that your card will not work, also try the card in slot two.

google "256K tds ram card hp48gx" and review the use of pinit and pinvar.

Cheers, Geoff

or wait for a 48GX expert, I have 4 and one with a 512K TDS card (see above post) and a 1MB card (HP) but I am by no means an expert 48GX user, I just fix them occasionally ;-)


Thanks Geoff,

I've seen some of the same posts. I've tried many of the suggestions. I need to download some data and try and store it to the card, I think.

Haven't tried pinvar...


I know there is a specific TDS site that walks you through a TDS RAM card set up. I was trying to find it and will still try if it has not been removed.

Cheers, Geoff

p.s. you replaced the battery, I know there is a program that keeps the GX on so the battery can be recharged. It defeats the timed turn off function but you do need a new set of batteries installed. It turns the calc on every 4 minutes and 55 seconds. Run it over night and the card battery will be fully charged. A new uncharged (or barely charged) battery will cause memory and card reading problems. Have you tried this?

pps this is all from memory (2 years ago!) and my battery has not been charged for awhile ;0)

Edited: 5 Apr 2011, 1:08 p.m.


There was no 2016 battery in the card when I got it. I replaced it with a new lithium 2016 a few days ago.

This is a different style card with a removable tray for the battery. I'll post some pictures tonight.

Edited: 5 Apr 2011, 2:34 p.m.


Okay, no pictures, but here's what made it work (for others if needed)

Card was made for 48SX. This was determined by the fact it was made in 91 and the GX came out in 93.

Given that, it needs a program call Super Switch installed (available on to switch between the two 128k banks. After this was installed AND some files were written to the two banks, the Invalid Card Data message stopped.

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