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RE: 20 ppm clock tolerance for WIS

Title: RE: 20 ppm clock tolerance for WIS


Information I have on oscillators/tolerances & pricing aligns well with your
findings. Although there may be up to a 2-3x price factor between 100 & 20
ppm parts, the absolute difference is in the 'used hubcap' realm. Something
that could be washed out over time with the large volumes of Ethernet ports.

Cross-linking to Henning's thread on reference clocks, I could then envisage
a 10GE LAN PHY card with a 156.25M +/-100ppm crystal or a 10GE WAN PHY
card with a 155.52M +/-20ppm crystal. I'm wondering what your view is for a
dual-mode UniPHY card. Obviously a 20ppm crystal also satisfies the LAN spec,
but a 730kHz swing is more than a crystal can be tuned, so it sounds like both
oscillators would be needed. That's about an extra square inch of board space, etc.