When it debuted, Serial ATA was overkill. Only the fastest (and most expensive) hard drives could utilise the extra bandwidth and by the time SATA II arrived, it was unnecessary for the average consumer. These days however, with affordable SSDs for desktops and a majority of notebook PCs sporting flash storage, even SATA III is being pushed to its limits. So what's the next step?
The Serial ATA International Organization, or SATA-IO, is already on the case with a new standard, called "SATA Express", as Anandtech's Kristian Vättö explains. With SSDs transfer speeds hitting — and exceeding — the gigabyte mark, SATA III, with its maximum rate of 600MB/s, is clearly not up to the task.
However, the other major bus standard in modern PCs, PCI Express, can handle this workload. With PCIe 3.0 sporting a maximum speed of 32Gb/s and even 2.0 capable of 16Gb/s, there's more than enough bandwidth to keep increasingly faster SSDs happy. That's where SATA Express comes in.
The hardware combines SATA signals with PCIe ones, with the resulting cabling resembling PATA gear of old, though the Anandtech article states the design is not final. As for the performance of the Franken-standard, it does exactly what it says on the tin, with tests showing a Plextor 256GB M6e SSD hitting its rated read speeds of 770MB/s, something not possible on SATA III.
The bad news is there's currently no mainstream support for SATAe from motherboard vendors and it might be a year before we see anything. Not that it's a big deal — for the regular person SATA III is good enough, but there are undoubtedly server configurations that would greatly benefit from the performance boost. For now, you can still use PCIe SSDs if you're desperate.
Testing SATA Express And Why We Need Faster SSDs [Anandtech]