On conducted topologies, here are two common ones where ln are variable attenuator legs.  The asterisk is a butler matrix or splitter/combiner in the relative center. 

A       B
  \     /     
l1\   / l2
    \ /
     *
    / \
l3/   \l4
  /     \
C      D

Then the power levels are controlled by variable attenuator legs, giving 4 degrees of freedom.

A       B
  \     /     
l1\   / l2
    \ /
     *
     | l5
     *
    / \
l3/   \l4
  /     \
C      D

This immediate above collapses to the star when l5 = 0.  Otherwise l5 separates two BSSIDs as an example.

The matrices are simple, eg. for the star:

1 1 0 0
1 0 1 0
0 0 1 1
0 1 0 1

Bob

On Tue, Nov 7, 2017 at 2:21 AM, Pete Heist <peteheist@gmail.com> wrote:
I ordered 2x APU2: http://pcengines.ch/apu2c4.htm

With 16GB mSATA SSDs, PSUs, cases and the serial cable I needed, the total came to 9097 CZK / 356 EUR / 412 USD.

Happily, the igb Ethernet driver for its i210 NICs does support BQL and appears to have hardware timestamping to boot. With three Ethernet ports, I’ll get one for management, one for testing and one for PTP time sync straight to the other APU.

I’m expecting the CPU PassMark (for what that’s worth) to be around 1100, 353 single core. That’s significantly less than other devices I was looking at, but at least it’s a quad core, and at this price it’s worth a try. Since Jon reported his E-450 (PassMark 769, 431 single core) was capable of line-rate GigE, hopefully this will be as well.

When they come I’ll run some benchmarks and report back how it goes…


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