A64 chip linux-sunxi wiki
The A64 is basically an Allwinner H3 with the Cortex-A7 cores replaced with Cortex-A53 cores (ARM64 architecture). They share most of the memory map, clocks, interrupts and also uses the same IP blocks. Differences between the H3 and the A64 seem to be: The H3 has three USB host controllers, whereas the A64 has only one. Both SoCs have an additional USB-OTG controller, which is assumed to be used as normal host controller as well. The H3 DRAM controller supports up to 2GB of RAM, the A64 supports up to 3 GB. Despite being a 64-bit chip, this makes the SoC entirely 32-bit on the physical side. The H3 supports 5 UARTs, the A64 has 6 of them. The MMC controller has been updated to support faster transfer modes. The MMC clocks have changed on the way, now the MMC controller itself provides support for the output and sample phase.