Why AHCI on 2013 - 2015 Retina series

[Faloude]

I'm wondering.. Why did Apple invest in manufacturing boards with PCI-e lanes which is probably more expensive than standard SATA and then choose to equip them with AHCI drives?

 

[venom600]

Because there weren't many PCI NVMe drives available then and the AHCI drives were still dramatically faster than SATA... the 2015 had remarkable drive performance for that time.