tnt4d ago

🎉 New video showing off running PCI express over COTS SFP modules and associated complications along with future plans.

And then a small side quest involving optical splitters and #ngscopeclient

https://youtu.be/XaDa9bBucEI

Definitely on the long side, sorry about that 😬 But I hope it's still interesting 🤞

Show threadKeenan Tims
@tnt Neat! How does clocking work if you don't send the clock and don't do clock recovery? Is the refclk not actually used by the receiver?
Apr 9 at 5:38amWeb
Show threadtnt2d ago

@ktims I provide an independent 100 MHz reference on the other side of the link. See my answer to @funkylab in this thread
https://chaos.social/@tnt/116362590463613892

There will also be more details in upcoming video when I deal with Spread Spectrum.

tnt (@[email protected])

@[email protected] Each serdes has some range it will lock in if close enough. When you think about it, 10G ethernet is also just data lane and a nominal rate. And the "skip ordered set" are dummy data inserted periodically that can be added/removed as needed to keep in sync when crossing domains. In Gen3 there is even something call SRIS "Separate Reference Independent Spread" where you can have independent SSC on each side. But seems specialized and couldn't get it to work so far. So no SSC for now.

chaos.social