It’s not about saturating the bus so much as the controller itself. SATA controllers can easily be overwhelmed by conventional non-SSD drives, try copying some large files from 3 drives to 3 other drives simultaneously. You’ll notice that despite the rated speed, the copy operations slow to a crawl. The best bus for SSD is PCIe and it shows in the 2-5x performance increase, however the price is significantly higher. It shouldn’t be but hey that’s how these guys make their money.
