Tauno Voipio  wrote:
> I'm just curious: What makes a Flash memory on an USB interface
> more durable than a Flash memory on a SD card?

Space.  A microSD card is very very space constrained.  It typically has a
stack of flash dice (eg 32 dice) bonded to a controller, that all has to fit
in the micro SD form factor, with very tight thickness constraints.
Additionally, the form factor limits its heat dissipation.  Typically the
controller doesn't have much local RAM, which is used for caching and
wear levelling.

A USB device isn't limited by the microSD form factor or heat budget, so
there's a lot more potential for using proper controllers sometimes with
dedicated RAM chips.  For example the Sandisk Extreme series (at least
the ones I've looked at) contains a full SATA SSD controller, with a SATA to
USB bridge chip on the front.  That's a lot more to fit into the package
than just slapping a simple flash controller onto a stack of NAND dice.

Theo

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