On Sat, Dec 03, 2016 at 05:39:08AM +0000, Duyck, Alexander H wrote: > There is no need for that. This is a Xeon E3-1220, note that there is no > v2-v? on the end of it. A quick look-up in ark.intel.com shows it has a gen2 > PCIe connection with 20 lanes on the CPU itself. > > In the case of the comment I would have to agree, another system might be an > option that has to be considered if you are hoping to get a full 40 Gb/s out > of the part. If however you are only planning to use it for one or maybe two > 10 Gb/s links you might be okay. That is all that message is really meant to > convey. Basically in the current configuration you aren't going to be able > to get optimal performance. > > Also you should probably be aware that you are going to likely put some > pretty serious stress on the memory system for the CPU. I would advise > making sure you are running DDR1333 and both channels populated as you max > out at about 21GB/s of total memory bandwidth for the CPU. With a 40Gb/s NIC > it becomes pretty easy to saturate the memory bandwidth on a small processor. > > There are other ways to work around the slot/bandwidth problem too. In > theory you could probably take a x16 PCIe gen3 capable switch and connect it > to the system. I've seen crazier things. The switch would then negotiate > down to x16 gen2 on the upstream ports and you could theoretically have x8 > gen3 on the downstream ports. Then again that would end up eating all but 4 > of the 20 available PCIe lanes on the CPU and that assumes that a x16 slot is > even available for something other than PCIe graphics.
Dear Alex, Thanks for your concern. This is a lab box for Q&A, so it's not that a problem that it has only PCI-e 2.0. >> [97789.169918] i40e 0000:01:00.3: PCI-Express: Speed 5.0GT/s Width x8 >> [97789.169923] i40e 0000:01:00.3: PCI-Express bandwidth available for this >> device may be insufficient for optimal performance. >> [97789.169926] i40e 0000:01:00.3: Please move the device to a different >> PCI-e link with more lanes and/or higher transfer rate. The thing is - the first line informs what the card got. The second informs about observed limitation. But the third is misleading - at least in this setup, and any other where all the slots are the same. Best Regards, Michał Mirosław ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ E1000-devel mailing list E1000-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/e1000-devel To learn more about Intel® Ethernet, visit http://communities.intel.com/community/wired
