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DateFri, 9 May 2008 22:20:06 -0400
FromBill Fink <>
SubjectRe: NIU - Sun Neptune 10g - Transmit timed out reset (2.6.24)
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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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