Broken SD cards - anybody got some?

[hamster]

Hi,

 

Does anybody have any broken SD / micro SD cards they could send me? I'm playing around with them at the moment and want to have a look at how they fail... and if using the SPI interface, clocking them slow, playing with voltages and/or keeping them cold can allow useful data to be extracted.

If anybody has one I would be really grateful if you could mail it to me... just PM me for my physical address.

 

Cheers

 

Mike

[alvieboy]

Define "Broken".

 

I think I know a guy with one that does not respond to any input. I think it would be of no use for any one.

 

Can you be more specific in the details ? You want physically damaged, logically damaged, or completely unresponsive cards ?

[hamster]

Anything where people anybody has gone "S%$t - that card is stuffed" and put it in a draw to gather dust.

 

In my (limited) experience most of them appear to be file system corruptions, and after re-formatting things seem to come right, but that might just be wear leveling on the card reallocating blocks. I get unexpected behaviour I usually salvage what I can using ddrescue, then put the card in the bin.

 

I have now started being interested in seeing how they die  - do they not respond at all? is it just contact on the interface pins playing up? (e.g. maybe oil or corrosion on the contacts) 

 

I also want to see if useful data can be read by managing the way they are access, and the operating conditions (hence my question about temperature ranges) - e,g, reading corrupt blocks over SPI at 200kHz at -20C

 

You see the occasional tale of people dumping them out using the SPI mode and an Arduino, but we have better tools than that :-)

 

I guess the worst possilbe failure mode would be if the SD card's internal block mapping tables get broken,. so it no longer knows what blocks are held where in the flash.