Modular System Architecture
Traditional communication and switch architecture leverages integrated designs in a single high-speed PCB, but this architecture is beginning to face signal integrity and thermal challenges at 56 and 112 Gbps PAM4. Samtec Flyover™ QSFP-DD solutions offer improved signal integrity and enable new modular system architectures, which also improve thermal efficiencies and lower costs. These next generation modular system architectures also enable greater design flexibility.
In this video, Jignesh Shah walks us through a demonstration which garnered much attention at OFC 2018. Two high-speed cable assembly demonstrations show impressive 112 Gbps and 56 Gbps long-reach cable performance. In the first, 112 Gbps PAM4 data is sourced from a Credo 112 Gbps PAM4 Pelican chip. This signal routes through ~ 12″ of 34 AWG, Samtec Ultra-Low Skew Twinax cable with Samtec FQSFP-DD and AcceleRate® connector systems.
The second, a 56 Gbps PAM4 signal, sourced from a Xilinx test chip with GTM transceivers, again through ~ 12″ of 34 AWG Samtec Ultra-Low Skew Twinax cable with Samtec FQSFP-DD and AcceleRate® connector systems.
The performance of both demonstrations is impressive: the BER of the first demo is 3e-7 pre-FEC, and the BER of the second is 5e-15 pre-FEC. More details of these demonstrations will be shared in an upcoming blog.
Great Interconnect Performance, But How Does It Work?
Designers agree that the signal integrity performance of these cable assemblies is excellent. But there’s always questions about thermal management, cable management, and of course cost.
Longer cables are easier to manage than shorter ones. As shown in the video, placing the ASIC further back in the chassis makes cable management easier. This placement has the added benefit of better thermals as it moves the power-hungry ASIC away from the temperature-sensitive front panel modules. The modular architecture allows for cost savings, as the ASIC module is the only high-speed PCB and is significantly smaller in size than the conventional design. The front panel and other PCBs can be simple FR4 with fewer layers. Further cost savings can be realized as retimers are not required.
The video also includes a thermal demonstration of the architecture. The 32 QSFP-DD’s can be powered from 7-14 watts, the ASIC can be powered to 500 watts, and the airflow can be modulated to 110 CFM.
The point of this demonstration is to show that Samtec high-speed products, design and system knowledge can be used to provide alternative, innovative solutions. If you want to explore this and other other possible solutions, please contact the HDR Group.