Memory card alternate sectors?
Posted: March 27th, 2019, 5:22 pm
Hello,
I'm not a regular here, so sorry if i've missed it, but i couldn't find anything in my searches:
Does anyone have any information about the alternate-sector area in the FAT block on the memory-card file system?
Sony's documentation (File Format 47.pdf) suggests to me that this must be some kind of spare area used to route around sectors that are no longer writeable. (Presumably it was implemented in the file system rather than in hardware like on modern flash devices for cost reasons?) But i've dumped several well-used cards of various sorts and i've yet to find any that touched this area. Furthermore, none of the third-party software i can find on the Internet (like MemcardRex) seems to account for it.
Some specific questions i have:
1. Is my understanding of this feature's basic purpose correct?
2. Is this something that ultimately went unused? Or is it just rare to encounter it in the wild?
3. If it *did* get used, how was it implemented? Did Sony's library functions handle all of it transparently, or did developers have to write their own code for it?
4. Are there any known limitations or edge cases surrounding this feature? For example: Could you map other sectors in the FAT block to the alternate-sector area, or just data blocks? Could you even map *other alternate sectors* to it? What happens when all of the alternate sectors are spoken for?
Eventually i think i might try to manually write some alternate-sector data to a card, read and write to it on the console, and then dump its contents again to see what it did. But i wanted to ask about it here in the mean time. Thanks!
I'm not a regular here, so sorry if i've missed it, but i couldn't find anything in my searches:
Does anyone have any information about the alternate-sector area in the FAT block on the memory-card file system?
Sony's documentation (File Format 47.pdf) suggests to me that this must be some kind of spare area used to route around sectors that are no longer writeable. (Presumably it was implemented in the file system rather than in hardware like on modern flash devices for cost reasons?) But i've dumped several well-used cards of various sorts and i've yet to find any that touched this area. Furthermore, none of the third-party software i can find on the Internet (like MemcardRex) seems to account for it.
Some specific questions i have:
1. Is my understanding of this feature's basic purpose correct?
2. Is this something that ultimately went unused? Or is it just rare to encounter it in the wild?
3. If it *did* get used, how was it implemented? Did Sony's library functions handle all of it transparently, or did developers have to write their own code for it?
4. Are there any known limitations or edge cases surrounding this feature? For example: Could you map other sectors in the FAT block to the alternate-sector area, or just data blocks? Could you even map *other alternate sectors* to it? What happens when all of the alternate sectors are spoken for?
Eventually i think i might try to manually write some alternate-sector data to a card, read and write to it on the console, and then dump its contents again to see what it did. But i wanted to ask about it here in the mean time. Thanks!