Thread:Talk:BeagleBone Black Extracting eMMC contents/BeagleBone Black Rev A5A/reply

Whether eMMC is mmcblk0 or mmcblk1 does not depend on hardware revision, it depends on kernel version and whether any μSD card is inserted at boot time. In principle it is non-deterministic since it depends on the order in which the devices are detected, but it seems that they respond quickly enough to make it depend on probe order only in practice.

I've patched my own kernel to make mmcblk numbering deterministic based on DT alias definitions, so mmcblk0 is then always μSD and mmcblk1 always eMMC. Robert Nelson merged these patches in his 4.9 kernel series.