Hello, I'm trying to re-mod my Wii. It was modded years ago and I wanted to start fresh. When running BootMii's nand backup, and it verifies, it can't verify one bad block. Does that mean the nand is bad or something? What do I do?
I have one bad block near the end of my NAND, too. BootMii's dump routine apparently doesn't pay any attention to the bad block map. If it didn't fail and you have a nand.bin it should be ok. BootMii copies the entire NAND instead of just the blocks allocated by the filesystem. (Like making an image of a HDD.)
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