How to set x8 lanes for x8 PCI-E Cards?

[Nima Gh.]

We have DL580 and DL380 servers and we attached PCI-E x8 Ethernet Cards to them. but they work at x4 mode! I just wanted to know how is it possible to set the lanes to work at x8 mode?

[Cederberg]

Which network card are you using?

Most network cards is PCI-E x4 but are compatible with an x8 slot. wich means that it will only use 4 lanes out of 8 if attached to a x8 slot.

Regards.
//Cederberg

[rick jones · Accepted solution]

If there are 8 lanes to use, a x8 card will use them. If only four lanes are shown being used by an x8 card, it suggests that the slot was only x4 "electrically" even though it is x8 "physically."

It is quite common for a ProLiant's PCIe I/O slots to be physically (ie the connector) 2x wider than they are electrically (the actual connections available). As the PCIe specs require cards to be willing/able to step-down to the available number of lanes this allows one to connect "larger" cards even if there aren't free slots available with that many "electrical" lanes.

[Nima Gh.]

Thank you! I attached it to a x16 PCI-E slut and it worked!!

[rick jones]

Just FYI, I'm reasonably confident that HP describes the slots based on their *electrical* lane width, not their physical width, so you put the card into what HP would call a x8 slot.

[Nima Gh.]

Thanks a lot!