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Posted by Ingo Thies on June 12, 2009, 7:19 am
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Hi,
I am not sure which is the best group to post this (and which one would
be the best to follow up). I've got a more general question about
(programmable) calculators using flash memory, particularly the Casio
FX-5800P (I own one) and the HP 48/50 (I know that they are completely
different worlds; maybe I'll buy one HP some day).
As far as I know, both are using flash memory to keep data even if the
battery is out. But flash memory has a limited number of writing cycles,
about 10,000 to 1 million. This rises the quetion in what situations the
calculator is writing to the flash. I can think of the following
possibilities:
1. every time a value is written into a variable (even during program
run) and every time a program has been edited,
2. every time a value is written manually or a program has finished
(last results),
3. only when the calculator is switched of, using RAM otherwise,
4. only if the battery is out or being removed, using some kind of
emergency power unit (maybe a capacitor).
I would guess that case 3 is the most probable (at least for the HP's)
since writing to flash is time-consuming and erodes the flash units. But
does anyone know how it is done exactly?
Regards,
Ingo
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Posted by Luke Morrison on June 12, 2009, 8:03 am
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show/hide quoted text
> Hi,
> I am not sure which is the best group to post this (and which one would
> be the best to follow up). I've got a more general question about
> (programmable) calculators using flash memory, particularly the Casio
> FX-5800P (I own one) and the HP 48/50 (I know that they are completely
> different worlds; maybe I'll buy one HP some day).
> As far as I know, both are using flash memory to keep data even if the
> battery is out. But flash memory has a limited number of writing cycles,
> about 10,000 to 1 million. This rises the quetion in what situations the
> calculator is writing to the flash. I can think of the following
> possibilities:
> 1. every time a value is written into a variable (even during program
> run) and every time a program has been edited,
> 2. every time a value is written manually or a program has finished
> (last results),
> 3. only when the calculator is switched of, using RAM otherwise,
> 4. only if the battery is out or being removed, using some kind of
> emergency power unit (maybe a capacitor).
> I would guess that case 3 is the most probable (at least for the HP's)
> since writing to flash is time-consuming and erodes the flash units. But
> does anyone know how it is done exactly?
> Regards,
> Ingo
I can't speak about the Casio model. But the Flash-based HP models
keep their Flash storage and their RAM storage totally distinct. The
Flash is used to store the core operating system, the Saturn emulator,
and the Saturn ROM image. Additionally, all objects stored in bank 2
("FLASH") are stored in Flash. Otherwise, all other stored objects,
as well as all items on the stack, are kept in RAM.
The contents in RAM are kept alive while the calculator is turned off
using standby battery power (either the main AAA batteries, or the
lithium backup batteries).
- Luke
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Posted by Daniel Oliva on June 12, 2009, 8:49 am
Please log in for more thread options I think flash memory is untouched unless you write/delete something
there (ROM upgrade, install a new library, or write any other object
to flash).
The calculator does not write to flash for normal operation.
No need to worry about that.
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Posted by Ingo Thies on June 12, 2009, 9:45 am
Please log in for more thread options Daniel Oliva wrote:
show/hide quoted text
> I think flash memory is untouched unless you write/delete something
> there (ROM upgrade, install a new library, or write any other object
> to flash).
> The calculator does not write to flash for normal operation.
> No need to worry about that.
Hmm, I can't speak for the HP 48/50, but the manual of the Casio 5800
says that the variables and program data are stored in the flash memory
to be kept even if the battery is replaced. The manual doesn't mention
any auxiliary battery.
So the flash is actually used in normal operation, but the question is
how often it is used. If only used on shutdown, then it might be ok (one
may estimate how long it will take to switch the calculator on and off
100,000 times (the number of write cycles typically given ob web sites).
If used 10 times a day with full memory (i.e. every flash bit used) on
average then it would take about 27 years to kill the flash. Most, if
not all, HDD drives die much earlier.
--
Gruß,
Ingo
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Posted by Joe Six-Pack on June 12, 2009, 10:52 am
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show/hide quoted text
> Hmm, I can't speak for the HP 48/50, but the manual of the Casio 5800
> says that the variables and program data are stored in the flash
> memory to be kept even if the battery is replaced. The manual doesn't
> mention any auxiliary battery.
Different manufacturers do things different ways.
HP machines use SRAM for operations associated with RAM (variables,
stack, programs etc.). Even extension cards are conventional SRAM that
needs a battery to retain their contents. Flash RAM is only used for
stuff that rarely needs writing to, such as the machine's firmware,
libraries etc.
If you want further details about how the Casio fx-5800 does things then
I suggest you ask in a more general newsgroup or in a Casio-specific
one. comp.sys.hp48 is not the best place for that.
Followup-To: set accordingly.
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> I am not sure which is the best group to post this (and which one would
> be the best to follow up). I've got a more general question about
> (programmable) calculators using flash memory, particularly the Casio
> FX-5800P (I own one) and the HP 48/50 (I know that they are completely
> different worlds; maybe I'll buy one HP some day).
> As far as I know, both are using flash memory to keep data even if the
> battery is out. But flash memory has a limited number of writing cycles,
> about 10,000 to 1 million. This rises the quetion in what situations the
> calculator is writing to the flash. I can think of the following
> possibilities:
> 1. every time a value is written into a variable (even during program
> run) and every time a program has been edited,
> 2. every time a value is written manually or a program has finished
> (last results),
> 3. only when the calculator is switched of, using RAM otherwise,
> 4. only if the battery is out or being removed, using some kind of
> emergency power unit (maybe a capacitor).
> I would guess that case 3 is the most probable (at least for the HP's)
> since writing to flash is time-consuming and erodes the flash units. But
> does anyone know how it is done exactly?
> Regards,
> Ingo