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eMMC is actually really different than SD in ways that matter for mobile devices. For example, eMMC supports a very low level hardware booting sequence (boot RO

eMMC is actually really different than SD in ways that matter for mobile devices. For example, eMMC supports a very low level hardware booting sequence (boot ROMs on SoCs can clock in data without needing a driver to initialize the eMMC device). Software drivers for MMC and SD add a lot of complexity. They need to query the device determine if it is eMMC, MMC, SD and then query the card status and properties and support quirky cards. MMC and SD have different specifications and initialization state machines (even though there is some overlap). I am not even going to mention secure boot. This is way much more complex than you might think.

userbinator 9y ago
For example, eMMC supports a very low level hardware booting sequence (boot ROMs on SoCs can clock in data without needing a driver to initialize the eMMC device). I know about that feature but the SoCs that use it are usually very primitive and not those in smartphones and the like, which have a much more featureful boot ROM. Keep in mind that even the Raspberry Pi can boot from SD, and that's not even a very powerful SoC. The MTK SoCs which I'm more familiar with have a boot ROM that supports booting from (e)MMC/SD, NAND, and USB/UART (for recovery). TI's OMAP series are similar: http://processors.wiki.ti.com/index.php/OMAP-L138_Preparing_SD_Card_for_Boot http://processors.wiki.ti.com/index.php/OMAP-L138_Preparing_...
- rvense 9y ago
  Freescale/NXP i.MX can too. The Novena has no soldered storage at all.