NOR "bad blocks"

Bernhard Priewasser priewasser at
Thu Oct 27 04:31:34 EDT 2005

> Not easily.  I haven't done the experiments myself, but wear-out
> effects were described to me.  Basically, you can write to a block and
> read it back out in a tight loop and things will never fail.  Not
> after 100k, not after 1M erases.  But if you write to the block and
> wait long enough, bits will flip.
> Bit-flipping will always happen from 0 to 1, similar to erases.
> Problem should be that the insulation around a flash cell has eroded
> and the charge will leak out over time - this cell is self-erasing
> now.

So this means that you have to hope that no block will wear out. And 
count on JFFS2's wear levelling.

What are the reasons that cause NAND blocks to die before they would 
"officially" wear out?
Dou you have a hint for good literature on this stuff (OK, let's better 
say NAND and NOR flash memory in general)?


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