I have a transcend 16GB SDHC card and a lot of photos on it that I'd like to recover. When I plug it into the SD card reader, it takes a while for the Mac to even recognize that there's a disk present, and it shows up as 1.07GB with geometry 520/64/63 (according to fdisk).

First I tried file recovery:

  • PhotoRec: no files are found (the images are in CR2 format and I'm using testdisk-6.14-WIP which claims to recognize that format under TIF)
  • dd / ddrescue: they create a 1.07GB image, same problem as above
  • TestDisk: doesn't find any partitions to recover

I found a source saying that the correct geometry for this type of SD Card is Heads 255, Sectors/Track 63, Cylinders 1953, so I tried manually setting that geometry in PhotoRec/TestDisk. No improvement.

Next I tried formatting the disk with fdisk. After writing and quitting, I ran fdisk again and it reported that the new format hadn't been saved on the disk. I also tried resetting the format/partitions with TestDisk and that failed also. The fdisk log is at this gist.

I don't really care about the card, I've already ordered a new SanDisk card. But I'd like to get the data off. Maybe, is there any way to force dd or some other tool to create an image of the disk based on the original geometry and not on what the card "thinks" its geometry is? Or am I missing something?

  • Why would you attempt to repartition/reformat if you want to recover the data?
    – Karan
    Oct 11, 2012 at 1:06
  • Reformat does not erase the data, just the partition table. My hope is that if I can correct the format, then the full 16GB of data will be accessible to a deleted file recovery app such as PhotoRec. (cgsecurity.org/wiki/PhotoRec) Oct 11, 2012 at 3:27
  • Have you tried using the card in a dif. card reader? The reader may be the issue and not the card. May be an easy way to at least get the data.
    – Carl B
    Oct 11, 2012 at 14:31
  • I've tried a few readers and they all show the same 1.07GB geometry. Oct 19, 2012 at 0:34
  • SD cards are not supposed to have a partition table. They're generally formatted with a single File System for the entire card (partitions are a way to put multiple File Systems on a single Volume)
    – MSalters
    Oct 22, 2012 at 13:49

2 Answers 2


I don't really have a clue as to the real problem here but I've got a recommendation. The other day my wife switched on our digicam and was told it couldn't access the sd card inside. I tried inserting the card into my MacBook - wasn't recognized. Then I tried with the old XP PC and a card reader - same result.

After searching the Internet I came across http://recoverfab.com/. Sent the card there by mail, got receipt confirmation three days later and recovery confirmation another three days later. As it's usually just the controller on the card that's broken and not the actual memory chips they disassemble the card and extract the chips. Then the data is read from the chips with a special device in raw format and compiled into something readable.


If you have electronic / programming skills, you can try to access SD card with SPI interface:

tiefpunkt tech - SD card recovery using an Arduino

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