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Thus far, our only experience with Intel’s platform controller hub code-named Patsburg is X79 Express. However, the same piece of silicon is also used as a foundation for the C600 chipset family.
We’ve long known that X79 didn’t expose all of the core logic’s integrated functionality. It comes close, but there’s an entire Storage Controller Unit that goes unused. Actually, that’s not entirely true. We recently saw ECS’ X79R-AX enable four SAS ports in Seven $260-$320 X79 Express Motherboards, Reviewed.
The PCH that ECS employs corresponds to the –B variant of C600. Otherwise identical to X79 (including the same 14 USB 2.0 ports, an integrated gigabit Ethernet MAC, eight lanes of second-gen PCIe, and HD Audio), the –B model officially adds four 3 Gb/s SAS ports to the four 3 Gb and two 6 Gb/s SATA connectors. Intel’s Rapid Storage Technology enterprise driver facilitates RAID 0, 1, 10, and, with the addition of a BIOS update, RAID 5 support with hardware-based XOR across the SATA ports. SAS is limited to RAID 0, 1, and 10, though you can add an upgrade ROM to get RAID 5 as well.
|Intel C600 Chipset|
|PCH-Based SATA 3Gb/s Ports||4||4||4||4|
|PCH-Based SATA 6Gb/s Ports||2||2||2||2|
|SCU-Based Ports||4 x SATA||4 x SAS||8 x SAS||8 x SAS|
|RSTe SATA RAID Support||RAID 0/1/10/5||RAID 0/1/10/5||RAID 0/1/10/5||RAID 0/1/10/5|
|RSTe SAS RAID Support||No||RAID 0/1/10||RAID 0/1/10||RAID 0/1/10|
|RST3 SAS RAID 5 Support||No||No||No|| Yes|
|Silicon-Based RAID 5 XOR||Yes||Yes||Yes||Yes|
|PCI Express 3.0 x4 Uplink||No ||No||Yes||yes|
Stepping up to the –D SKU doubles SAS connectivity to eight ports. Add that to the PCH’s native SATA and you end up with two 6 Gb/s ports and 12 3 Gb/s ports. Now, consider that C600 connects to one Xeon E5 processor via DMI 2.0—a four-lane PCIe 2.0-like link with 20 Gb/s of bidirectional throughput. That's a bottleneck just waiting to happen. So, Intel connects the PCH's SCU directly to four PCIe lanes hijacked from one of the processors, alleviating traffic from the storage controller.
The flagship –T version is functionally identical (including the eight SAS ports and four-lane uplink), only it includes RAID 5 support for the SATA and SAS ports, too. It’s not clear how much of a premium stepping up through the C600 hierarchy adds to Xeon E5-ready motherboards. However, if you were planning on buying an add-in HBA or RAID controller anyway, the option to get much of that functionality on-board is certainly convenient.
If you don’t need any of that fancy stuff, there’s a baseline –A model with four SATA 3Gb/s ports and six SATA 6Gb/s ports, four of which are tied to the SCU. It still supports RAID 0, 1, 10, and 5, and it includes hardware-based XOR, too. There’s just no SAS connectivity.