Channel Analysis for a 6.4 Gb s−1 DDR5 Data Buffer Receiver Front-End

Stefanie Lehmann, Friedel Gerfers
2017 Advances in Radio Science  
<p><strong>Abstract.</strong> In this contribution, the channel characteristic of the next generation DDR5-SDRAM architecture and possible approaches to overcome channel impairments are analysed. <br><br> Because modern enterprise server applications and networks demand higher memory bandwidth, throughput and capacity, the DDR5-SDRAM specification is currently under development as a follow-up of DDR4-SDRAM technology. In this specification, the data rate is doubled to DDR5-6400 per IO as
more » ... 00 per IO as compared to the former DDR4-3200 architecture, resulting in a total per DIMM data rate of up to 409.6<span class="thinspace"></span>Gb<span class="thinspace"></span>s<sup>−1</sup>. The single-ended multi-point-to-point CPU channel architecture in DDRX technology remains the same for DDR5 systems. At the specified target data rate, insertion loss, reflections, cross-talk as well as power supply noise become more severe and have to be considered. Using the data buffer receiver front-end of a load-reduced memory module, sophisticated equalisation techniques can be applied to ensure target BER at the increased data rate. <br><br> In this work, the worst case CPU back-plane channel is analysed to derive requirements for receiver-side equalisation from the channel response characteristics. First, channel impairments such as inter-symbol-interference, reflections from the multi-point channel structure, and crosstalk from neighboring lines are analysed in detail. Based on these results, different correction methods for DDR5 data buffer front-ends are discussed. An architecture with 1-tap FFE in combination with a multi-tap DFE is proposed. Simulation of the architecture using a random input data stream is used to reveal the required DFE tap filter depth to effectively eliminate the dominant ISI and reflection based error components.</p>
doi:10.5194/ars-15-157-2017 fatcat:u6y4q6h7ifchjfuh2zsxr6bntm