HP 41CV memory module

[hth]

(11-30-2020 10:50 PM)rprosperi Wrote:  Definitely not. When you encounter a MEMORY LOST, all data, programs and settings are lost, including ExtMem, Key Assignments, etc. I don't know if all RAM contents are in fact set to zero (I suspect they are) but all pointers and settings are reset to the same as initial power-on condition.

They are reset to zero. However, here is where it gets interesting. It is noted in a comment in the firmware that they do not need to be reset the whole memory range, but HP did not dare to do it.

When I made my update for larger extended memory, I faced the problem that it takes a good amount of time to clear 15-16 pages of memory compared to 4 (which also takes a moment or two). I decided to change it to only clear page 0 and 1 (as suggested in the comment). This clears the base module of extended memory and all normal data registers, but not the additional extended memory modules. This makes master clear twice as fast compared to earlier.

This works the same way as when you insert an extended memory module, which will contain garbage in it once inserted and there is no code to clear such module (apart from the one doing the master clear). Pointers in the base module tells if the extra modules has been initialized and it never peeks into them to see if they contain anything interesting (garbage). It will always write something before it reads anything in these additional extended memory modules.