The best consumer SATA III SSDs today become saturated at about 500MBps, according to Jim Handy, an analyst with Objective Analysis.
It's not a surprise, Handy said, that Apple settled on PCIe, as the price for the controllers are already approaching those of SATA controllers.
"If they both cost the same, then why use SATA?" Handy said in an email reply to Computerworld.
Looking forward, Janukowicz said he expects to see more PC makers using PCIe/NVMe drives, but he doesn't expect them to be broadly available until later in 2017. Handy believes M.2 PCIe SSDs will "sweep" the new PC market within two years. But a lot of the PC SSD market will be upgrades to older PCs, "so SATA will remain strong in that market for the next 5+ years," he said.
A big question is whether higher performance in an SSD will make much difference to an end user, Handy said.
Most PC programs and data fit comfortably within a system's DRAM memory, so there are few disk input/output (I/O) requests made from the main storage. That means that the only time users will notice the difference between a PCIe-based and SATA-based SSD will be when the system boots, and when a new program or file is being loaded, Handy said.
"The performance difference will be the smallest for file loads, since most users' files are pretty small (like 1-5MB). Loading a program will be more noticeable, but still not a big difference, since most programs' splash-screens are timed to remain active long enough for the user to read them," Handy said. "So that leaves boot. Not something to write home about!
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