There seems to be some confusion between PCIe and SATA Express. They are both quite different.
[B]PCIe[/B] (PCI Express). Every modern PC has PCIe. It’s a high speed connection for connecting things like a graphics card, and can use up to 16 PCIe generation 3 lanes to get the required performance. To get an SSD to work on this system bus requires a Non-Volatile-Memory (NVM) controller to communicate between the NAND flash layer and the PCIe system bus, and drivers to make it all work.
The RevoDrive 350 uses a proprietary NVM layer called VCA2, and connects to PCIe using 8 PCIe gen 2 lanes, so the max available bandwidth available is 4GB/s.
The NVMe specification should soon make an appearance in SSDs, where all SSD that comply with the specifications should work with a single unified driver. NVMe doesn’t use AHCI, so should be far more efficient than SATA Express.
[B]SATA Express[/B], is SATA over PCIe. It still uses the AHCI layer, and at the moment appears to be limited to 2 PCIe Gen 2 lanes, so has a max bandwidth of 1GB/s without overheads. With overheads you can expect around 800MB/s max.
On Intel’s soon to be released Z97 chipset, they appear to have combined two SATA 6Gbps ports and added a (keying) connection to achieve SATA Express. This is at the expense (when SATA Express is used) of sacrificing 2 SATA 6Gbps ports.
If SATA Express is not used, then you can use these ports (minus the keying port) to bring the count back up to 6x SATA 6Gbps ports.