SSDs with PCI Express interfaces are still relatively rare. So are SSDs with three-bit TLC flash. However, according to market research firm TrendForce, we'll see many more of both kinds of drives next year. The company's DRAMeXchange division says that PCI Express will supplant Serial ATA as the interface of choice for high-end systems. Windows 8.1 already offers native support for NVM Express, an interface specification designed specifically for PCIe SSDs. Intel's upcoming Broadwell platform will reportedly support the standard, as well, helping to accelerate the adoption of PCIe gear.
We may not see Broadwell on the desktop until late next year, so PCIe drives could be scarcer in full-sized form. That said, DRAMeXchange predicts that PCIe solutions will become more popular the following year and that they'll have "a legitimate chance of becoming the mainstream PC SSD format in 2015."
On the flash front, the transition three-bit TLC flash will reportedly begin in earnest. DRAMeXchange cites Samsung's "widely praised" 840 EVO for inspiring multiple SSD vendors to develop "similar products that are geared towards 2014." Those drives will likely be lower-end offerings, the press release says, in part due to the more limited endurance of TLC NAND. We've observed in our SSD Endurance Experiment that three-bit flash is indeed more fragile than the two-bit MLC NAND found in most consumer-grade SSDs. We've also seen that modern TLC drives can take an awful lot of writes before wear becomes a problem—enough that we wouldn't shy away from three-bit drives on endurance grounds alone.
Unfortunately, TLC NAND hasn't really delivered on the lower prices that were supposed to be enabled by its higher bit density. Samsung's TLC-based 840 EVO rings in at $165 for 250GB and $570 for 1TB. That's definitely at the budget end of the scale, especially per gigabyte, but MLC drives can be had for about the same price or cheaper. Crucial MLC-based M500 is down to $145 for 240GB and $510 for 960GB. Both are limited-time deals (and the 960GB drive requires a promo code, AFNJ3007, to get to $510), but a look at Newegg listings confirms that plenty of other MLC drives are within striking distance. If three-bit flash is destined to become more prevalent, let's hope the next wave of drives lowers prices appreciably. At least then, we'd be getting something in return for sacrificing endurance.