HP48GX Expansion

[SteveH]

I've just gone back to using my HP48GX after using some of my other HP calculators for a long while.

I'm wondering what's the advice on whether it's worth expanding the memory or not. Are expansion cards getting thin on the ground and expensive? Once I start adding programs am I likely to benefit from expansion?

[Han]

(05-26-2017 10:24 AM)SteveH Wrote:  I've just gone back to using my HP48GX after using some of my other HP calculators for a long while.

I'm wondering what's the advice on whether it's worth expanding the memory or not. Are expansion cards getting thin on the ground and expensive? Once I start adding programs am I likely to benefit from expansion?

Unless you are using the HP48GX as a data collector, you probably only need to get two cards: a 128KB for card slot 1, and 2MB for card slot 2. In truth though, I have never filled the 2MB card beyond 2-3 banks (i.e. only about 512KB to 756KB were used), mostly archives of stuff that I usually had as backups for card slot 1.

[SteveH]

Thank you Han

Are there particular cards worth looking out for or just buy the HP ones?

[Han]

The HP Brand ones will tend to be more expensive, followed by the data-collecting brands (e.g. TDS and SMI to name a few). After those come the PCB-only type of cards -- basically a PCB with all components exposed.

I own quite a number of memory cards and I actually find that the PCB-only cards are the most economical, and arguably more reliable. The major brand name cards (including HP) often come with better safeguards such as the retractable metal plate that supposedly guards the connector pins when the card is not inside the HP48GX. However, over time, these guards are the very reason for card issues -- they can sometimes cause shorts. I have had to even tape my HP 1MB card's metal guard to prevent it from coming down because it would often cause a short and the end result would be total destruction of data.

The other advantage of the PCB-only cards is that the PCB is generally very thick -- with components, they tend to be almost as thick as brand name cards. This means that they are very sturdy and will not bend over time. The brand name cards have much thinner PCBs because they are housed inside a metal casing. Over time, these cards can actually bend, causing contact issues. The glue inside them can also deteriorate, and then you have to fix them with epoxy or be left with a card whose casing could come apart.

PCB-only cards are also more likely to be battery powered. TDS and SMI have rechargeable batteries in some of their cards. I can only wonder what happens when those rechargeable batteries eventually die. HP cards and PCB-only cards have easy-to-replace batteries (fortunately).

The only drawback (for me) with the PCB-only cards is that they tend to not have an easy way to remove the cards. The brand name cards have a tab glued to the outside of their cases. While nice, even an HP brand card (stored in pretty much perfect conditions), have had their tabs "droop". One of my 128KB HP cards had its tab "slide" down to almost halfway. It is brand new, and was stored in a vertical position. I have now turned the box upside down in the hopes that it will eventually "slide" back to its original position so that I can then store the box and card laying flat.

[rprosperi]

(05-26-2017 05:17 PM)SteveH Wrote:  Thank you Han

Are there particular cards worth looking out for or just buy the HP ones?

These NORAND 128KB cards work great, and at only $50USD are FAR cheaper than you'll find for any HP-branded cards.

http://www.ebay.com/itm/292128706749

[Chris Dreher]

There are also FRAM cards, available sometimes on eBay in 128KB and 512KB sizes. These are also bear circuitboard cards. Unlike a normal RAM card that requires a small battery to preserve data when the card is removed, a FRAM card does not require a small battery to preserve its data. The downside is that FRAM is a new technology and thus these cards cost more that typical. Also, because FRAM is new technology, some folks are unsure about it.

There is a long thread about HP48 FRAM cards here: http://www.hpmuseum.org/forum/thread-6562.html

FYI, I have not tried out any FRAM cards to verify them but suspect they are just fine to use.