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I have seen several forum posts (link 1, link 2) debating whether eMMC offers an endurance advantage over SD cards for embedded applications.

My understanding was that the write endurance problem is an inherent feature of all Flash storage technology, and that there is only a nominal control interface difference between Micro SD cards and eMMC chips.

I am aware that there are differences in write endurance due to the structure of the Flash storage itself. As I understand it, this is essentially a trade-off between storage density and write endurance, where Triple Level Cells (TLC) have higher capacity than Single Level Cells (SLC), and Multi Level Cells (MLC) somewhere in the middle.

I can understand how write endurance is tied to this internal flash structure, but I don't think the write endurance has anything to do with whether there is an SD or eMMC interface on the front end.

Is this correct? Or am I missing something?

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  • \$\begingroup\$ Just speculation. The file system may be structured differently. A poorly designed (for Flash) file system may require writing a directory or FAT space for each file update, resulting in higher wear (more Write cycles) on that space. A better one may distribute that wear evenly, prolonging life. I don't know if these two differ in this respect, but that's one area I'd look. \$\endgroup\$
    – user16324
    Jan 7, 2020 at 22:03

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I can understand how write endurance is tied to this internal flash structure, but I don't think the write endurance has anything to do with whether there is an SD or eMMC interface on the front end.

The interface is determined by the controller the NAND cells are hooked up to, so putting an eMMC controller on a flash cell doesn't make it more reliable than if you'd hooked up an SD controller. Each cell still has the same endurance, although different controllers can of course implement different wear leveling.

The usual concern with SD cards however is the large number of fakes out there, which sometimes find their way into even legitimate products. In that sense, if you're buying higher endurance parts, it may be easier to find what you're looking for in an eMMC package or at least to be sure that your product has the part you think it does once it goes into production.

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    \$\begingroup\$ Another relevant consideration for many embedded devices is that eMMC will be more robust than an SD card, physically speaking. An eMMC chip soldered to the PCB will have much better vibration resistance than an SD card stuck into a slot. It will also be more secure, since it can't be easily removed. eMMC also has a smaller footprint. And, while the flash memory's characteristics are the primary driver of speed, the tight clearance between the eMMC chip and the PCB reduces unwanted inductance and signal distortion, which tends to allow higher data-transfer rates than SD cards. \$\endgroup\$ Jan 9, 2020 at 4:06

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