Collaboration reduces cost of PCIe 4.0 comms over twinax cable

In a joint demonstration, PLDA’s PCIe 4.0 IP and Samtec’s FireFly micro flyover interconnect system delivered PCIe 4.0 speed without the use of retimers or updated motherboard using Megtron 6 technologies, significantly reducing cost, reports Samtec.

The combined PCIe 4.0 solution delivers full PCIe 4.0 bandwidth (16GT per second) over copper or optical fibre at minimal cost.

The demo combined a PLDA PCIe 4.0 acquisition board running PLDA’s PCIe 4.0 controller IP with Samtec’s FireFly Micro Flyover System. It could suggest a solution to overcoming the inherent limitations of maintaining PCIe 4.0 performance over long distances without changing the motherboard technology or using costly retimers, says Samtec.

As cloud computing and deep learning accelerators drive faster advances in the PCIe roadmap, existing hardware designs cannot support the higher speed signals over the same distances. The PCIe 1.0 specification allowed signals to travel as much as 20 inches over traces in mainstream FR4 boards, even while passing through two connectors.

In contrast, the quicker 16GT per second PCIe 4.0 signals will peter out in under six inches and without going over any connectors. In today’s designs, PCIe 4.0 signals can only travel three to five inches, requiring costly redesigns, moving to Megton 6 and adding a retimer for increased distance.

This demonstration used an alternate approach, with optical fibre (330 feet) or Twinax Flyover systems (10 inches) to deliver PCIe 4.0 x4 with no significant loss of bandwidth.

The demo showed a system running at 16GT per second and displaying relevant throughput and latency measurements. The demo result shows the bandwidth is not impacted by distance when using copper or optical fibres.

By using optical fibres, PLDA and Samtec demonstrate that PCIe 4.0 can be used for remote applications (e.g. EMI sensitive environments)

“PCIe Designers are delaying their upgrade to the next generation of PCIe because they anticipate high board manufacturing costs, said Hugues Deneux, COO of PLDA. “With this demo, we want to show a new approach that provides great bandwidth and good latency over any distance for PCIe 4.0 communications.”

“Samtec and PLDA’s multi-year PCIe 4.0 collaboration lowers barriers of entry and quickens time to market,” said Arlon Martin, senior marketing director of Samtec Optical Group. He added: “The Samtec PCIe® Optical Flyover Cable Assembly enables designers to more efficiently take advantage of the incredibly low latency and high throughput without board constraints”.

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