Hooray for nice hand-me-down SLR cameras! I finally have a better camera than the one built into my (now ancient) Samsung Galaxy S II that I use for pictures on this blog. The camera, a Canon EOS 50D, had an 8GB CompactFlash card that I was preparing to erase and reuse, and had problems trying to read out the card’s contents; a few stubborn files would refuse to copy and Explorer would simply hang until I restarted the program or unplugged the card. Additionally, when using my Hard Disk Sentinel program to do a surface scan, it too would freeze when reading a certain sector on the card.

Instead of using a USB-to-CompactFlash adapter (I could not find my card reader and have not seen it for over a year now, come to think of it) I used a CompactFlash-to-PATA adapter, then a PATA-to-SATA adapter so I could directly hook up the card to my computer. In addition to having greater theoretical throughput, it allows me to view the S.M.A.R.T. diagnostic data that the card provides.

Memory card issues and performance

The diagnostic information doesn’t really provide any insight into the health of the card; none of the S.M.A.R.T. attributes are listed as critical, and many of them are listed as vendor-specific. Oh well, at least it gave me some sort of information…

After finding a copy of the card’s contents on my home server (I seem to have previously backed up the card before the corruption occurred but didn’t recall doing so until I had raked through some of my archives), I decided I’d do a full card erase and see if it would cause the card to be usable again. I called up the Surface Test in Hard Disk Sentinel and used its surface-write tool to erase the user-accessible area of the card. A few blocks seemed to write dramatically slower than the rest and repeated write tests did not resolve their sluggishness; I call shenanigans with the memory card’s controller and its reluctance in reallocating problematic sectors…

The card itself isn’t very fast. The sequential I/O of the card is good enough for casual photography, but I would definitely not use this card in an embedded system that uses a CompactFlash as a sort of mini-SSD; even though it shows up in my system as a hard drive (non-removable), its random I/O is quite sluggish and its random write speed is worse than that of a standard hard disk drive.

Teardown

The card itself is a sandwich of aluminum plates, a plastic case and the PCB assembly that holds the controller, Flash memory and the CompactFlash connector. A hobby knife run under the aluminum plate was able to separate the plate from the plastic body; some glue and a couple clips were the only things holding the card together.

The card’s controller is a Phison PS3006, which sports a PCMCIA (and therefore CompactFlash) interface with True IDE (or plain PATA) support. It contains an 8051 microcontroller core with a few components to assist with interfacing with the Flash memory, such as a hardware ECC (error correction code) engine and a small amount of SRAM for a buffer.

The datasheet for the PS3006 doesn’t provide information on the S.M.A.R.T. attributes, nor does it indicate what type of Flash wear-leveling is provided. Given the controller’s limited computing capabilities, I’m thinking it uses a less-complex but less-reliable form of wear leveling, known as dynamic wear leveling (see Micron’s application note for more information). It’s less capable of dealing with memory wearout, but doesn’t require the computing overhead of static wear leveling (which proper SSD controllers use to keep performance up).

The memory is an Intel 29F32G08AAMD2 device, which is an asynchronous MLC NAND Flash memory chip. There are two installed on this card with another two footprints on the PCB being unpopulated, suggesting that the 16GB version of this card has all four footprints populated.

Conclusion

Given the simplicity of the card, I don’t really have much else to add about this card. Either way, it’s lost my trust with regards to holding my photos. I bought a NOS Disk 16GB CF card from Amazon as well as a SanDisk Extreme 32GB, and plan to use the latter to hold my photos, with the former mainly being a simple curiosity of the construction of a card from a lesser-known manufacturer. Hopefully those will also provide S.M.A.R.T. data, as I prefer Flash-based storage devices with some sort of S.M.A.R.T. data capability. (Is it an insatiable thirst for knowledge? A means of doing regular ‘check-ups’ on my storage device? Probably the latter, but maaayyyybe the former as well. 🙂 )