X550-T1 in PCIe 2.0 x4: Does it run at 10 GbE?

ReturnedSword

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Jun 15, 2018
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The Intel X550-T1 specification states it uses a PCIe 3.0 x4 slot, however in my new PC (Ryzen 2700X), I'd like to use it in the PCIe 2.0 x4 slot if possible.

The NIC should be backwards compatible with earlier revisions of PCIe.
  • PCIe 3.0 x4: 3.94 GB/s - 31.52 Gb/s
  • PCIe 2.0 x4: 2 GB/s - 16 Gb/s
Even accounting for overhead, it seems like a PCIe 2.0 x4 slot should have plenty of bandwidth for a single port 10 Gb/s NIC.

Is anyone running such a configuration? Does the NIC negotiate its full speed?
 

hjfr

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Nov 21, 2013
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The NIC will negotiate at 10 Gb, no problem. There is no relation between NIC negotiation and pci-e speed.

In theory, pci-e v2 speed is 4 Gb per lane. So for pci-e 2 4x : 16 Gb/s.
A 10 Gb NIC at full speed (full duplex) requires 20 Gb/s bandwidth
A speed test in one direction will problaby be ok (running at max speed). But, a speed test in full duplex mode (10 Gb/s each direction) will be limited.

pci-e v3 port would be better for use all possibility of 10 Gb full duplex.
 

ReturnedSword

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Doh, I forgot about dull duplex!

If that's the case I would install it in the second PCIe 3.0 x16 slot.

I've read mentions that one can get a fake X550-T1/T2 on eBay. Is this widespread? How would one check for an authentic card?
 

EffrafaxOfWug

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PCIe links are also full duplex so a PCIe 2.0 4x will be fine with a single 10Gb NIC. In any case only if it were single, four lanes at 500MB/s each is 2GB/s and 10Gb/s is less than 1GB/s.
 
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fohdeesha

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A 10 Gb NIC at full speed (full duplex) requires 20 Gb/s bandwidth
A speed test in one direction will problaby be ok (running at max speed). But, a speed test in full duplex mode (10 Gb/s each direction) will be limited.

pci-e v3 port would be better for use all possibility of 10 Gb full duplex.
PCI-E is full duplex, an x4 slot is 16gbps of full duplex bandwidth, a speed test in both directions on a 10gbe card would only use 10gbps of that
 
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hjfr

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You're right.
Pci-e is also full duplex. Thx for correction.

So, pci-e 2 4x port will be ok for one 10Gb port.
 

i386

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10Gb/s is less than 1GB/s.
10gbe and faster use the more efficient 64b/66b encoding, 10GBit/s should give you ~1.155 GByte/s raw bandwidth.Even with overhead from the different protocols you should get more than 1 GByte/s throughput.
 

mrkrad

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as long as that slot is connected to the cpu directly and not through a shared dmi/qpi/IF connected chipset!
 

billc.cn

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as long as that slot is connected to the cpu directly and not through a shared dmi/qpi/IF connected chipset!
On Ryzen platforms, the PCI-E 2.0 x4 slot is provided by the chipset, but the latter connects to the CPU via a PCI-E 3.0 x4 connection, so should be fine.
 

EffrafaxOfWug

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10gbe and faster use the more efficient 64b/66b encoding, 10GBit/s should give you ~1.155 GByte/s raw bandwidth.Even with overhead from the different protocols you should get more than 1 GByte/s throughput.
Sorry yes, schoolboy error on my part as I'd done my maths backwards - 10Gb/s is of course 1.25GB/s raw bandwidth on the carrier, as you say probably 1.2-1.2GB/s data throughput once overhead is taken into account.

Still no sweat for a PCIe 2.0 4-lane setup though.
 

ReturnedSword

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On Ryzen platforms, the PCI-E 2.0 x4 slot is provided by the chipset, but the latter connects to the CPU via a PCI-E 3.0 x4 connection, so should be fine.
Yes, that's right. The PCIe 2.0 x4 slot is slot -> chipset -> CPU.

Now I just have the issue of nBase-T 10 GbE switches being quite expensive and loud :D