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    SubjectRe: NIU - Sun Neptune 10g - Transmit timed out reset (2.6.24)
    On Sat, 10 May 2008, Jesper Krogh wrote:

    > Rick Jones wrote:
    > >
    > > Into which slot was the Neptune inserted? (sure will be nice to have
    > > Alex Chiang's pci slot id patch in mainline one of these days :)
    > >
    > > Is that slot x4, x8, x16?
    >
    > I can find out excactly .. on monday. But shouldn't x4 be enough anyway?
    > wikipedia says 250MB/s pr. lane. And no slots is less than x4, so I
    > thought that it didn't matter to me.

    No you need 8x for 10-GigE. The 250 MB/sec per lane is 2 Gbps per lane
    so 4x is only 8 Gbps. For a typical PCI-E transaction size of 128 bytes,
    and PCI-E protocol overhead of 20 to 24 bytes, that takes off about 20%,
    which leaves you with about 6.5 Gbps of usable bandwidth, which is further
    reduced somewhat by the required PCI-E ACK and flow control packets that
    accompany the actual data transaction packets. I am not an expert on
    PCI-E but I believe this info to be generally correct.

    -Bill


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