On 5/26/2010 1:32 PM, Willard Korfhage wrote:
Neither side was forced to a particular speed and duplex, so it auto-negotiated
to 10 full. This is a sudden change, as of a couple days ago, with no changes
on my part. I'm wondering now if maybe the cable developed an intermittent
connection. If one of pins 4, 5, 7 or 8 failed or was intermittent, then it
couldn't run gigabit, and I would see this sort of behavior. I'll replace the
cable when I have access to the machine and see if that fixes it.
Yes, a crummy cable might do it.
But there is *another* possibility, depending on the peer.
I've heard of approaches where network node could select a lower speed
(e.g. 10FDX) to save power. Running a PHY at 10 Mbps consumes a lot
less power than 1000 or even 100 Mbps. In fact, when systems using
Intel AMT suspend, and potentially other systems that enter S3 suspended
state, they automatically place the NIC in a lower speed mode to reduce
power consumption.
Of course, when the NIC comes back on (e.g. at system resume) or when
load conditions demand, then the NIC should return back to full 1G.
- Garrett
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