On Sun, 2013-10-20 at 01:15 +0200, Petar Bogdanovic wrote: > On Sat, Oct 19, 2013 at 10:52:07PM +0000, Waskiewicz Jr, Peter P wrote: > > > > The quick history behind it is we implemented it on 10GbE first, where > > no spec existed for auto-negotiation for 10GbE-1GbE with fiber. We had > > optics modules that could do either 10 or 1 GbE, but no link-layer > > mechanism to autoneg the speed. So we implemented it in software and > > got it working, and called it SmartSpeed. This is a backport to other > > parts that can benefit from the same methods. > > I tried to disable SmartSpeed back then when I did all the testing but > was not able to identify a straightforward change that didn't involve > modifications of things I don't fully comprehend. > > Was that a bad idea to begin with or could disabling SmartSpeed help?
Disabling SmartSpeed will cause the link negotiation to rely on the physical layer to negotiate the link properties. This isn't necessarily a bad thing, because link negotiation on 1GbE devices should be solid. However, there are devices out there that don't conform to the specs, which I suspect you're running into. Intel does quite a bit of compatibility testing of our parts, and there are cases where we find link partners that don't conform to specs for link negotiation. In those cases, link either never gets established, or the link speed is degraded. SmartSpeed is designed to help you at least get link, rather than just fail since the link partner either doesn't implement the spec (which is bad), or is flat out broken with regards to the spec (which is also bad). In a nutshell, if you disable SmartSpeed, you can uncover link partners that don't behave according to spec. Leaving SmartSpeed enabled will allow you to get link, but it may mask the underlying problem of a misbehaving link partner. Hope this helps clarify, -PJ ------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60135031&iu=/4140/ostg.clktrk _______________________________________________ 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
