NAND Backup

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BootMii FAQ
Why do I have all of these "bad blocks"? Can I fix them?
This is completely normal; in order to bring down the price of NAND flash chips, all manufacturers will allow chips to leave the factory with a small number of bad blocks. It's similar to bad pixels in LCD panels -- it would be too expensive to throw away the whole panel (or in this case, the whole chip) due to a few bad pixels. With NAND flash, software usually remaps these blocks so you don't even notice, but BootMii works at the lowest level possible so we have to take these into consideration when writing our code. There are 4096 blocks; according to the flash chip manufacturer, at least 4016 blocks are valid (in other words, up to 80 blocks may be bad). Reference: datasheet, page 19