ASUS Z97-A LGA1150 Motherboard Review

Author: MAC
Date: May 7, 2014
Product Name: Z97-A
Part Number: Z97-A
Warranty: 3 Years
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SATA Express & M.2 Through Flex IO

While there may not be many additions to Z97 from a functionality standpoint, the porting of Intelís Rapid Storage Technology into the PCIe interface has some major implications for the PCHís storage subsystem. First and foremost, it has allowed motherboard manufacturers to incorporate M.2 and SATA Express onto their boards.

Both M.2 and SATA Express are rolled into the new SATA 3.2 specification which was ratified last year. Both use a combination of standard SATA and a PCI Express bus alongside AHCI and NVMe interface standards for an ultra fast 10 Gbps data pathway. That represents a major performance uplift in comparison to current SATA 6Gbps drives.

The implementation of SATA Express and M.2 has been achieved through the use of Intelís Flexible IO interface. Essentially, the PCH houses a total of 18 ports which are split into three predominant groups: four SATA, six PCIe 2.0 and four USB 3.0 which make up the main connectivity options. The PCIe ports are typically used for connection to third party controllers or providing secondary PCI Express functionality to supplement the motherboardís primary x16 slot(s).

Flex IO steps into this equation by providing four additional ports that are configurable. #5 and #6 can be used for either a pair of PCIe 2.0 lanes or USB 3.0 while ports #13 and #14 are either PCIe 2.0 or SATA 6G. The only limitation here is the Flex ports have to be paired up and maximum number of PCI Express lanes canít exceed eight. This means if #13 and #14 are configured for PCIe, #5 and #6 will need to use USB 3.0 and vice versa.

On some boards, these additional Flex I/O ports will be combined with the six static ports and paired up with a PLX port multiplier to deliver an additional eight PCI-E 3.0 lanes for triple GPU support. This means sacrificing dedicated bandwidth towards Thunderbolt, additional networking capabilities and other controllers

Motherboard builders can use those configurable Flex IO ports and provide a two lane PCI Express 2.0 interface to a compatible SATA Express / M.2 controller. This grants SATA Express and M.2 a theoretical bandwidth of 10Gbps but both interfaces canít be used at the same time; itís either one or the other. In addition, due to PCH limitations, there is a lack RAID compatibility, though some boards will use a PCI-E multiplier chip and support up to two SATA Express ports. RAID is still possible through the use of two M.2 drives running in parallel within a secondary enclosure thatís linked to the motherboard via the SATA Express interface.

As you might expect the implementation of these high speed storage standards is completely different when moving from one board to another. For example, some motherboards will disable secondary PCI-E slots when either an M.2 or SATA-E drive is detected while others will use the aforementioned port multiplier approach so the storage interfaces remain independent of other functions.

With all of this talk of high speed interfaces, there are still some limitations here. Since Intel has limited the Z97ís PCI Express lanesí bandwidth to the 2.0 standard, any SATA 3.2 devices will be granted only a fraction of their available bandwidth without the use of expensive bridge chips and other, more exotic solutions. While dual lane controllers are the norm now, quad lane units which double the available bandwidth will be available in the coming months. This could leave Z97ís version of SATA Express and M.2 at a distinct disadvantage against add-in-board style PCI-E drives which can use more lanes and thus provide significantly higher performance.

Another bit of good news here is the backwards compatibility of SATA Express with the existing SATA 6Gbps standard. Since the SATA-E port is composed of two SATA connectors alongside a plug for the PCIe communications, its two 6Gbps connections can be used for standard drives as well.

M.2 meanwhile is essentially a small form factor version of SATA Express that is compatible with Intelís Smart Response Technologyís caching or it can be utilized as a primary storage interface. Due to the costs involved in higher capacity M.2 SSDs, we canít see this being used as a primary means of storage for most systems. However, it could be extremely beneficial in the mATX and mini ITX markets where space is at a premium.

Another big question lies in Z87ís lack of SATA Express and M.2 support. There isnít anything stopping Z87 motherboards from incorporating either of these but since the SATA 3.2 standard was ratified so close to that Lynx Pointís rollout, the necessary controllers and associated SSDs werenít available until only recently. That means most Z87 boards didnít include M.2 ports until the architectureís final months. SATA Express was left off the table entirely due to Intelís lack of PCIe-based support in their Rapid Storage Technology software stack. This has all changed with Z97 so weíll likely see M.2 and SATA Express, both cornerstones of the SATA 3.2 interface, quickly become defining features.

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