CM500 slow connection

[glen-m]

I am paying comcast for 300Mbps that they recently upgraded to 400Mbps. I have never gotten much more than 200Mbps on my older MacBook Air hardwired through an Apple Airport Extreme. My son's Acer Predator does usually get about 300Mbps also hardwired through the Airport Extreme. Today I checked and I am getting about 90Mbps from all computers. I tried directly connecting to the CM500 and still get 90. I tried resetting the modem, having Comcast reset the gateway, restarting all devices, changing the ethernet cables. No luck. Always stays at 90Mbps. Here is the report. Any help would be appreciated.

[antinode]

> [...] getting about 90Mbps from all computers. I tried directly
> connecting to the CM500 and still get 90. [...]

   Ask the OS on one of your "all computers" about the speed of its
Ethernet interface.  It should be able to negotiate a 1Gb/s rate with
the Ethernet interface of the CM500, but if all it gets is 100Mb/s, then
you could have a damaged connector, or (partially) fried port, or bad
cable.  All eight conductors are needed for 1Gb/s; only (the right) four
for less.

"directly connecting" what?

> [...] I have never gotten much more than 200Mbps on my older MacBook
> Air hardwired through an Apple Airport Extreme. [...]

   200Mb/s is more than 100Mb/s, so that couldn't be cable- or
interface-limited.

> [...] changing the ethernet cables. No luck. Always stays at 90Mbps.
> [...]

   Look at the LEDs and the reports from the software.  Identify the
bottleneck.

> Cable Model CM500 status 210213.pdf

   My cable-TV-modem expertise is nil, but I'd expect 16 happy channels
to do better than 100Mb/s.