have you ever withnessed calculators not working anymore due to corrupted memory?

[PANAMATIK]

(05-02-2017 06:41 AM)pier4r Wrote:  Dave with corrupted I mean "consistently reporting wrong (previously stored) data from all or certain memory sectors, even after a reset" or even not working at all.

Why is illogical to use the rom? I mean libraries are stored there (at least for 48,49,50) and if one needs extra space as temporary working space the rom is the only viable way. Surely it is not common (I can barely fill the memory of my 50g), but someone may have done it. Especially the 48 series as far as I know is pretty low on ram.

ROM is "Read Only Memory" per definition, it cannot be used for changing contents like RAM. But you are right, in todays calculators Flash memory is used instead of genuine ROM memory and it can be used for changing contents but has limited number of write cycles.

To understand the possible answers to your question you have to know about the interaction of Boot memory, Flash memory and battery buffered and non buffered user RAM memory. Modern calculators use all of these memory types. The Boot memory normally is protected flash memory, which cannot be overwritten accidentally.

It is principally possible, that corrupted memory in each of the above type can lead to permanent malfunction. If (and really If) the boot memory contents is still intact then it is possible to recover the calculator by an update.

Wrong battery buffered RAM contents (and even uninitialized RAM if it is not cleared at power up) can lead to a not working calculator. It depends solely on the operating systems initialization procedure. if the operating software is not water proof and depends on the RAM contents at start up, it can easily run into an endlesss loop or else. Performing a Reset procedure should avoid this problem, because it clears all RAM contents and this can be handled by the non water proof operating software (until the memory becomes corrupted again by some complicated user actions).

Wrong Flash memory leads always to unpredictible behaviour, if it concerns the operating software. But normally wrong Flash contents will be covered by the bootloader, which checks its checksum before jumping into it.

Wrong Bootloader memory is the worst case. If the bootloader isn't present any more, the operating software will not be started and it inhibits any update. Only special programming tools at the manufacturer can be used to restore the calculator.

Bernhard