HP41CX Memory

[Garth Wilson]

(07-17-2024 02:15 PM)Bballreich Wrote:  Garth, Monty, thanks very much for the reply. So, if the CX can handle a couple of Xmem modules, and each module contains 238 registers, then total available memory would be 320 + 238 + 238 for a total of 796 registers? Again, I'm new to all this stuff, so please be patient with me! Thanks again for the help!

As Kim says, EXTended memory is more like an internal hard disc, unlike main memory (although there are modern modules that change that).  Main memory is 319 registers (with 7 bytes per register), and the Extended-Functions/Extended Memory module that's built into the cx gets you started with 124 registers of extended memory and you can add two more modules of 238 each, for a total of 600 registers of extended memory.  Again, this is separate from the 319 registers of main memory.

I had the good fortune of coming across a double extended-memory module on eBay years ago for a good price.  EduCALC (and perhaps another distributor or two) used to sell a few different combined modules, and I also got a combined HP-IL/Extended-I/O module when I bought my first 41cx in 1986.  These of course save ports; but today there are ones that let you have lots of ROM module images in the flash memory of a single module.)

There are others on this forum who know the 41's insides a thousand times as well as I do.  I'm just an intensive user who got into the 41 originally as a handheld controller for equipment on the workbench.  You can see my story at http://wilsonminesco.com/HP41intro.html .