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I've been working recently on a Supermicro X9QR7-TF+/X9QRi-F+ server. I took the user's manual and saw two things: the chipset is Intel C602, and the expansion slots are PCIe 3.0.

According to Intel's website C602 chipset supports PCIe 2.0.

Furthermore, the user's manual states:

The C602 chipset provides extensive IO support, including the following functions and capabilities: (1) PCI-Express Rev. 2.0 support (2) PCI-Express Gen. 3 uplink supported by some SKUs

What does "uplink supported by some SKUs" mean? So does it support Gen3 or not?

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If SuperMicro says their implementation supports it, and Intel says it's available on some SKUs (that is, some specific versions of the chipset), then I don't see any reason to believe why that server wouldn't support PCIe 3.0

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  • Thanks, just wanted to make sure. I have a SSD that is connected to the PCIe slot with some annoying bandwidth issues. Double check that it is connected to a PCIe Gen3 is the first thing that came into my mind. – Gilsho Mar 16 '16 at 15:15
  • often the driver software will tell you exactly what a PCIe/NVMe SSD is connected to - certainly the Intel ones do – Chopper3 Mar 16 '16 at 15:39
  • I'd check dmidecode (assuming Linux) as well, it should tell you the PCI version. – zymhan Mar 16 '16 at 15:57
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What does "uplink supported by some SKUs" mean?

I would assume that it means on some variants of the chipset the "uplink" (that is the connection from the chipset to the CPU) can be PCIe gen 3.

So does it support Gen3 or not?

AIUI all the downstream PCIe ports on the chipset are PCIe gen 2. The upstream link from the chipset to the CPU may or may not be gen 3.

However the PCIe slots on your motherboard are not connected to the chipset! They are connected directly to the CPUs. The CPUs each have 40 PCIe gen 3 lanes available (of which your motherboard only uses a small fraction).

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Alright, this is a very old question. I found the answer in Intel C600 Series Chipset Datasheet, Section 5.3.

The PCH contains up to 8 PCI Express* root ports and one uplink port. All versions of the PCH contain the 8 root ports. The Intel® C606, C608 Chipset SKUs contain a x4 uplink port while the Intel® C602, C602J, C604 Chipset and Intel® X79 Express Chipset SKUs do not. The purpose of the uplink port is to provide a direct path for the SAS controllers, SGPIO used by the SAS controllers, and SMBus ports to the processor/ memory without having to be multiplexed onto the DMI bus and sharing bandwidth with the rest of the component. The uplink port is not connected to the downstream root ports.

So the PCIe uplink is not used by the PCIe slots connected to the PCH, instead, they are used by SAS SCU and extra SMBus on C606 or C608 chipset. The answer is clear, PCIe slots provided by any C60X PCH will never support Gen3.

Motherboards using C606 or C608 chipset are what SuperMicro calls some SKUs. For example, X9DRi-F and X9DR3-f share the same design, but the "i" model uses C602 while the "3" model uses C606.

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