Is it possible to use a 1MB card one the 48SX

[rprosperi]

TDS made 256K and 512K cards for the SX and they work reliably. I have heard rumors that they also made 1MB cards, but have never seen one or even evidence they existed (price sheet, EduCalc Catalog, etc.).

These cards use 2 or 4 128K banks, but unlike those in the the 48GX, a special library must be installed, which has commands to let you switch/select the banks; only one of these banks is available at a time and this bank is always 'seen' by the SX as either Port-1 or Port-2 (based on where it is physically installed). But note that you can change banks under program control so access to this extra memory can be easily automated.

The library for switching can be found here:

https://www.hpcalc.org/search.php?query=...ch+library

There is no documentation, but the commands are easy to figure out.

On eBay, these cards are often listed as "48GX only", but you can tell which TDS (Tripod Data Systems) cards are this SX-compatible type by looking at the copyright date, conveniently printed on the bottom front of the card. All the cards I have (and have seen) are "Copyright 1991", which is 2 years before the 48GX was even introduced. They are not labeled as 48SX only, as at the time, the 48SX was the only machine that existed that used these cards.