PRIME: Memory Map



#5

Is there a memory map for the Prime?
I am interested to see where various things are located in a general way,not really specifics.
Is a backup of the OS actually on the calculator at all times to re flash the OS or is the OS transferred to the calculator using the Connectivity Kit from ones PC after the flash memory has been re formatted?
Is there more than one layer of memory.
For example one layer where the backup copy of the OS resides to use in reinstalling the OS,etc
Are the different areas of memory walled off from others so that, for example, memory for programs can not be corrupted by say variable storage,etc.


#6

There is no "re-installing" of the OS. The OS sits in a pre-defined location, and any "formatting" done excludes these pre-defined locations. Theoretically, nothing the user does will ever affect those memory blocks in which the OS is stored, including formatting.

There is an INI file here: Old HP Prime firmware

This will give you an idea of certain memory boundaries.

As for memory boundaries for programs and variables, I am under the impression that they all share the same block.

Lastly, there is RAM and FLASH. RAM is for use by the calculator like RAM on a PC. Flash is where the OS is stored, as well as user variables, settings, programs, etc. It serves the same purpose as a hard drive on a PC. My understanding is that nothing is "saved" into flash until the HP is turned off -- this is why there is a slight delay when turning off the HP. It is writing to FLASH before it shuts down.


#7

Quote:
There is no "re-installing" of the OS. The OS sits in a pre-defined location, and any "formatting" done excludes these pre-defined locations. Theoretically, nothing the user does will ever affect those memory blocks in which the OS is stored, including formatting.

There is an INI file here: Old HP Prime firmware

This will give you an idea of certain memory boundaries.

As for memory boundaries for programs and variables, I am under the impression that they all share the same block.

Lastly, there is RAM and FLASH. RAM is for use by the calculator like RAM on a PC. Flash is where the OS is stored, as well as user variables, settings, programs, etc. It serves the same purpose as a hard drive on a PC. My understanding is that nothing is "saved" into flash until the HP is turned off -- this is why there is a slight delay when turning off the HP. It is writing to FLASH before it shuts down.


When HP gets an upgrade to the OS ready, will the new version of the OS be written to the pre-defined location you mention above, using the connectivity kit and erasing( or over-writing) the older version of the OS?
In the saving you mention above is there only saving if there is something different or is the saving a complete copy of the calculator state at the time of turning off the calculator.?


#8

Quote:
When HP gets an upgrade to the OS ready, will the new version of the OS be written to the pre-defined location you mention above, using the connectivity kit and erasing( or over-writing) the older version of the OS?

My understanding is that is exactly what happens.

Quote:
In the saving you mention above is there only saving if there is something different or is the saving a complete copy of the calculator state at the time of turning off the calculator.?

Unfortunately, I do not know the answer to this one. Since flash has a limited number of writes before we can expect degradation in integrity of the data, I imagine that the algorithms limit the number of writes -- so that only the updates are saved. This probably means some sort of garbage collection is necessary. All this is pure speculation, though.


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