I notice that flashrom erases many pages even if they are already erased. I've gotten curious: does erasing erased pages count as a 'write cycle' against that page?
ron
On 16.05.2009 23:27, ron minnich wrote:
I notice that flashrom erases many pages even if they are already erased. I've gotten curious: does erasing erased pages count as a 'write cycle' against that page?
AFAIK yes for some chips (maybe not all).
Part of my plan for flashrom is to read the chip before any write/erase action. Checking if the flash is already erased is one of the possibilities.
Regards, Carl-Daniel
ron minnich wrote:
I've gotten curious: does erasing erased pages count as a 'write cycle' against that page?
It probably counts as an erase cycle.
Writing runs a large current through cells, storing some charge in what is essentially an insulated conductor. http://en.wikipedia.org/wiki/Hot_carrier_injection
Erasing also runs a large current through cells, but in reverse, to empty out the stored charge. http://en.wikipedia.org/wiki/Quantum_tunneling (good graphics here) http://en.wikipedia.org/wiki/Fowler-Nordheim_tunneling
I haven't found if a flash cell fails because of the repeated exposure to high currents when writing or erasing, or because of the charge transfer that occurs when a cell changes value.
Even if re-erasing an erased cell can be assumed to not be as harmful as erasing a programmed cell, it will still have an impact on the lifetime of the cell. Maybe it is negligeable though.
If the important wear is in fact not high currents, but rather charge moving into or out of the store, as supported by the likening of that process with an ionization radiation effect, then re-erasing will not have much of an impact on the lifetime because no charge has to move around in the cell.
Tom - do you know?
//Peter
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Carl-Daniel Hailfinger -
Peter Stuge -
ron minnich