This is where Mac accessory and upgrade specialist Other World Computing (OWC) comes in. So even though Apple's machines from 2013 through at least 2016 (depending on the model) included the fastest storage that money could buy at the time, those systems have been left behind as the NVMe storage market has matured from an exotic high-end novelty into the technology that's rapidly displacing SATA for mainstream computing. Apple's PCIe SSDs used a proprietary form factor rather than the M.2 standard that went on to become the standard for client PCIe SSDs. Apple's earliest PCIe SSDs used the AHCI protocol for compatibility with existing operating systems, but hardware compatibility was a very different story.
Apple was an early adopter of PCIe SSDs, introducing them in 2013 when the NVMe specification was still in its infancy and before any NVMe hardware was available.
