[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)




The way the Flash chip works, you have to erase either the whole chip, or
whole sectors (sectors vary in size between 8K (only two of these) and 64K
(most are this size)).  This is what wears the flash (and what causes your
screen to dim...noticeable especially on HW1 TI-92's and TI-89's ... but
also on the 83P when you're loading a new OS) and there's not much way to
get around it.  So, if you need to *set* any bits on the sector, you're
going to have to erase it.  If you wanted to set some bytes to zero, you
wouldn't have to erase first.  You can reset bits whenever you like, but a
set requires an erase.

Hope that's clearer (erase loading 0FFh causes some mix-ups in terminology),

-Dan Englender



----- Original Message -----
From: "Kirk Meyer" <kirk.meyer@colorado.edu>
To: <assembly-83@lists.ticalc.org>
Sent: Monday, July 09, 2001 12:43 PM
Subject: [A83] Re: What is the problem with flash writes (in general)


>
> I'm just curious.. wouldn't it prolong the life of the Flash ROM to reset
> only those bits that need to be reset to store the byte that's to be
stored
> there? For example, to store $00 in Flash wouldn't require reseting
> anything. I don't know much about the hardware so maybe a reset in this
> fashion isn't possible.
>
> -----Original Message-----
> From: assembly-83-bounce@lists.ticalc.org
> [mailto:assembly-83-bounce@lists.ticalc.org]On Behalf Of Dan Englender
> Sent: Monday, July 09, 2001 10:35 AM
> To: assembly-83@lists.ticalc.org
> Subject: [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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