[NTLK] Storage card specifications

[Bradley Loeding]

Unfortunately, Flash will eventually lose its data just sitting in a drawer.
Sad but true. The information is stored, not physically, but as trapped
electrons whose presence or lack thereof on each cell's floating gate
determines the logical state of the bit.

Just as you can tunnel electrons onto the gate quickly at elevated
potentials, so too do they slowly leak away. This is a quantum effect and is
temperature dependent, among other things. You'll get a wide opinion as to
how long it will take before enough of the buggers shuffle off and drop each
cell below sense threshold.

www.cl.cam.ac.uk/~sps32/*Data*Rem_CHES2005.pdf
(2nd page)

One major flash manufacture specs its passive data retention at only a
decade. Some chip fabs claim 50-100 years, which is a bit hard to believe.
Truth is, no one really knows, but I'd personally get a bit nervous after
15-20 years.

Ironically, we can store the Library of Congress many times over on a single
drive, yet the next generation won't be able to read it without active
maintenance of the data... If anyone wants true long-term storage, break out
the pen and ink.

-Bradley



On Thu, Apr 7, 2011 at 8:06 PM, Dan <dan at dbdigitalweb.com> wrote:

> Hmm as I understood it, Flash basically was "burned" into the substrate
> and this substrate wears out eventually after being cleared and
> rewritten to.  Hence the information/state change does not eventually
> "leak away".  Of course there are probably more types of Flash and this
> is probably true of some of them (perhaps the old bubble memory type?).
>  Although unless there has been damage to the Flash memory or just
> wearing out, I haven't heard of Flash loosing its data.
>
> But of course feel free to correct me if I am wrong here.
>
> -Dan
>
>