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I browsed the datasheet [1] for the BCM2711 processor and did not see an eMMC controller on this part. Assuming the SD card is connected by SPI which would explain why it's so slow. Also rules out eMMC.

[1] https://datasheets.raspberrypi.org/bcm2711/bcm2711-periphera...

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The Raspberry Pi Compute Module 4 has eMMC.

Jeff Geerling benchmarked it and found it faster than his fastest SD card: https://www.jeffgeerling.com/blog/2020/raspberry-pi-compute-...

It's definitely not NVMe fast, but it's perfect for average workloads.

Weird. So the processor has an eMMC controller but they left that out on the datasheet.

The publicly-available datasheets for the SoC in the Pi are incredibly, and as far as I can tell intentionally, incomplete. The SD card controller is just one of the things lacking public documentaiton.

The physical layer for eMMC is SDIO- the same is used for SD cards, at least if you want more than ~ a megabyte/s of interface bandwidth.

IIRC the layers above SDIO are slightly different for eMMC and SD(HC), but generally SoCs that have SDIO interface support both types of memory.

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