I’m looking at doing a rewrite of the OS9 DrivePak driver, and I am not certain how some of my ideas will be effected by the microSD life expectancy. I know that I can pretty much expect a minimum of 100,000 erasures over the surface of each device which, with the assumed added bonus of autonomous wear leveling, should yield an impressive life span. Even so, I want to keep an eye toward extending this as much as I reasonably can.
Right now the driver reads and writes its data from/to the 1st 256 bytes of each 512 byte sector. The remaining 256 bytes are discarded when reading, and a value of $ff is written. When flash memory is erased a value of $ff is written into each memory location. Now if a bit is already set when it is erased, is there any “wear” on that bit? I think there is not. Can anyone confirm or refute this with any authority?
If there is never any wear on that 2nd half of the sector then it might be conceivable to make a 2GB card, being used as a 1GB card, last twice as long.
Thanks in advance for any help you can give me.
This post was submitted by hhos.