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SD Memory Cards at a Crossroad

 John Geldman
Description: New NAND technology: Restating the obvious at Flash Memory Summit: Cutting edge NAND technology is complicated and varies significantly by NAND vendor, Without SDA specification evolution, SD cards might run out of NAND sources. Support for new native erase block sizes and multiples of native erase blocks (for parallel operations) was essential for video capture performance: New native erase block sizes are evolving with NAND technology, However, infinite Card option complexity was at odds with Host simplicity, But we all negotiated and compromised...End-users should never need to know how the sausage was made, other than that SDA engineers found a path for going forward. How can it be less expensive and faster? Optimal performance is when all the card’s resources go saving into the data stream with zero write-amplification (one data, one write, one time); Creation of a minimized set of building block sizes and a new set of rules for using these sizes helps this work: Hosts restricted enough choices to enable design qualification, Card makers approved enough choices for future NAND evolution. The draft allocation sizes run from 1 MB to 512 MB, and such large building blocks now can be used to efficiently hold multiple recordings. How can it be less expensive and faster? Simplicity! SDA specifications ‘evolved’ – the rules for different capacities (e.g., SDXC) – the rules for different interface speeds (e.g., SD UHS II) – the rules for different speed classes (e.g., C10, U1), But this left hosts and cards with a collection of rules to implement for each capacity/interface/speed class combination. The new design acts identically across capacities and interface types for easier adoption.
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Domain: Electronics
Category: Photo
Contributing Organization: Flash Memory Summit
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This presentation shares unreleased capabilities of an
uncompleted SDA specification.
While the described features have reached consensus,
the specification has not been completed or ratified.
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Flash Memory Summit 2014
Santa Clara, CA


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John Geldman
19 September, 2015