I have a dual Xeon board with Intel C602 chipset and two E5-2670 CPUs. The board comes with five PCIe 3.0 x16 slots and a PCIe 3.0 x4 slot; all of which are directly connected to the CPUs.
I added a PCIe 3.0 card to a x16 slot connected to the first CPU ("BSP") as well as another card to the x4 slot (also connected to BSP). In both cases I find the that they are downgraded to PCIe 2.0 speed.
# lspci -vvs 82:00.0 | egrep '(82:00|GT)'
82:00.0 Non-Volatile memory controller: Samsung Electronics Co Ltd NVMe SSD Controller SM981/PM981 (prog-if 02 [NVM Express])
LnkCap: Port #0, Speed 8GT/s, Width x4, ASPM L1, Exit Latency L1 <64us
LnkSta: Speed 5GT/s (downgraded), Width x4 (ok)
LnkCtl2: Target Link Speed: 5GT/s, EnterCompliance- SpeedDis-
# lspci -vvs 02:00.1 | egrep '(02:00|GT)'
02:00.1 Ethernet controller: Intel Corporation Ethernet Controller 10G X550T (rev 01)
LnkCap: Port #0, Speed 8GT/s, Width x4, ASPM L1, Exit Latency L1 <16us
LnkSta: Speed 5GT/s (downgraded), Width x4 (ok)
How may I assess why the link speed was downgraded and possibly rectify the problem?
Best Answer
Have you tried reviewing the BIOS, I have found a few times now you can set the PCI-E slots to either work on revision 2.0 or 3.0. If its set to 2.0 in the BIOS the cards will only work at 2.0 even though the card and slot theoretically both support 3.0.
Mike