They may be trying to invoke the remapping technology of the formatting process.
Solid state memory can be "read" an unlimited number of times with no "wear" to the media, but a "write" is a destructive process. Each time you "write" to a location, the operation technically damages the location (very slighlty, but it does.) Normally an individual location should be able to handle tens of thousands (perhaps even hundreds of thousands) of writes before it goes bad, but you can have random locations that go bad significantly sooner than others.
Original flash media didn't use "memory leveling" and that meant the some memory locations were used much more than others... think of magnetic recording tape where you are recording music of different lengths... the tape at the beginning of the reel is always being re-written, but the last tiny bit of tape on the real is almost never used. The same concept applied to early solid state media.
The "leveling" technology tries to use all locations on the card evenly. It basically re-maps what the card thinks of as it's first available memory address so that it's not technically the first available physical address on the card and that way all locations on the card get used about the same amounts and this extends the life of the card.
If a location is actually going bad, a low-level format should hopefully pick it up. A high level format doesn't actually write to every address on the card and zero it out... it merely declares all space to be free. A low level format is supposed to "test" each location on the card by performing a write operation to make sure it actually works. I suspect the camera's built-in "low level" checkbox on the format option doesn't _really_ do a low-level format because it all happens FAR too quickly to have technically tested every location on the card and I think THIS is why they suggest formatting on the computer.
In any event, if it detects a bad location, it typically does not notify you, it simply marks it as a bad location so that the card will never attempt to write to that location again... and moves on.
So my guess is they're trying to do a few low level format cycles to get the offending bad location(s) marked as bad so that the card will stop using any marginal memory locations and behave as expected again.
BTW... both physical hard drives as well as solid-state memory both have bad blocks or bad memory addresses even when brand new. But the formatting process is supposed to identify and mark those locations -- using alternate locations instead.
Tim Campbell
5D III, 5D IV, 60Da
