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Most CF Cards Fail DMA Transfers

Posted by kdawson on from the it's-all-in-the-controller dept.

Anomalyst writes "In his quest to create an open source video camera, Andrey Filippov of elphel.com has determined that most Compact Flash devices, although claiming to be DMA capable, do not perform Direct Memory Access transfers correctly. This means successful movement of data to and from the device takes much more time with DMA disabled." The culprit appears to be the controller chip packaged with most of the CF cards Filippov tried. We last visited Elphel and their work on open source digital cameras in 2002. Filippov gave a Tech Talk at Google last year.

3 of 140 comments (clear)

  1. Re:Lexar and Sandisk should be good by LanceUppercut · · Score: 5, Interesting

    How do you know that it indeed works in a full-fledged UDMA mode and not in some half-assed workaround mode, used specifically because of the problems in question existing in the cards' controllers. Did you reverse engineer the camera's firmware?

  2. CF inside the cameras do not use "True IDE" mode by AndreyFilippov · · Score: 5, Informative

    In the article I was only describing CF working in "true IDE" mode, inside the cameras thy usually do not use it, so do not care much about the problem I've got. But it is important if you try to connect the camera with a simple adapter instead of the HDD

  3. Re:Compact Flash by AndreyFilippov · · Score: 5, Informative

    Two of the reasons wewrw already mentioned: 1 - I've got IDE interface "for free" in from the processor chip, just needed connector. 2 - CF cards are higher capacity. 3 - I can download CF and ATA specs from the Internet, while SD (when I checked it) was much more difficult to get.