Chip I/O as in having lots of memory channels and lots of PCIe lanes. That said, Intel mobile CPUs don't have fantastic I/O either, this will matter more when

Chip I/O as in having lots of memory channels and lots of PCIe lanes. That said, Intel mobile CPUs don't have fantastic I/O either, this will matter more when Apple has to scale up to iMac Pro/Mac Pro territory. "SSD performance" is a very high-level view of I/O, and depends more on the size and configuration of flash chips used than the CPU design.