[A83] Re: What is the problem with flash writes (in general)

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[A83] Re: What is the problem with flash writes (in general)


There was a big huff about MirageOS writing to the Flash when it first came
out.  Just to get things straight, MirageOS does *not* write to the Flash
every time you start or exit MirageOS.  It only does so when you change
options or create folders.  The rest of the time it reads from the AppVar
directly from Flash ROM (and doesn't use port 7, *smile*).


And yes, the 1,000,000 should be for erase cycles.  Actually writing to the
Flash doesn't do much to it, it's erasing it that's the issue.  The flash
(or parts of it) is erased during garbage collections, defragments, and OS
loads.  You may be wondering if writes are no problem, why do we need to
erase the Flash to begin with?  Well, when you"write" to the Flash ROM, you
can only reset bits, you can't set them.  When the Flash is erased, it's set
to all 0FFh, after which the bits can be reset as you want them.  Say you
need to set one bit on one byte of the Flash ROM?  You need to erase the
whole sector and rewrite the whole sector with the changed bit.

-Dan Englender


----- Original Message -----
From: "Michael Vincent" <hookman@worldnet.att.net>
To: <assembly-83@lists.ticalc.org>
Sent: Monday, July 09, 2001 12:29 PM
Subject: [A83] Re: What is the problem with flash writes (in general)


>
> Programs/apps already write back to flash for storage. Take MirageOS, for
> example, it stores its settings in an AppVar which is archived upon
exiting.
> Direct writing to the flash would be dangerous, even if it was possible,
> because you lack the VAT structure to track variables then. As for the
> minimum of 1,000,000, that's for erases, not writing. (not sure about
this).
>
>
> Michael Vincent
> Detached Solutions - www.detacheds.com
> Radical Software - www.radicalsoft.org
>
> ----- Original Message -----
> From: "james l" <james@kirk.math.twsu.edu>
> To: <assembly-83@lists.ticalc.org>
> Sent: Monday, July 09, 2001 9:22 AM
> Subject: [A83] What is the problem with flash writes (in general)
>
>
> >
> > Not really that no one has been able to do them in their programs, but
the
> > fear of failure.
> >
> > "Minimum 1,000,000 program/erase cycles per sector
> guarantead" -Am29F400B.pdf
> > (amd's tech doc on it)
> >
> > Writing to it for everything, would be a hazard, but having programs do
> > write-back to the flash for storage, shouldn't hurt at all. (if we could
> do
> > it)
> >
> >
> > Just my .02USD
> > James L.
> >
> >
>
>
>
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