Most CF Cards Fail DMA Transfers

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.

Comments

Re:Lexar and Sandisk should be good

[AaronW]

It would not be possible to get the performance the camera gets if it did not use DMA mode. It may be that it uses 1K blocks like the article says they used for a workaround. The cards also work fine in UDMA capable external readers, otherwise I would be seeing a ton of messages in the camera forums I frequent. Sandisk and Lexar UDMA CF cards are frequently used with the new cameras that can support it and are widely used by professional photographers.

Also, the article said that the Sandisk card they tried worked. They did not mention anything about Lexar but did mention problems with Transcend, which is not certified for my camera.