The Asymmetric Crosstalk Harnessed Signaling (ACHS) scheme [1]–[4] provides a significant improvement to the original Crosstalk Harnessed Signaling (CHS) technique [5]. This paper presents a study of design optimizations applied on 3D multilayer interconnect arrangements [2] [3] [6], in which alterations on the encoding matrices or the distribution of wires in the channel translate into a modification of the bit encoding regions and their associated performances. While ACHS has been presented as a vastly superior signaling option than the originally proposed CHS due to the elimination of the highly sensitive common encoding eigenmode [1], further encoding optimizations on the critical (worst performing) data bits and the strobe inside the ACHS implementation can further improve the bus performance. This work presents a full set of performance comparisons involving data and strobe bits, on a ACHS-encoded bus with channels adjacently routed in 3- and 4-layer 3D interconnect arrangements.

This paper presents a novel scheme based on the Crosstalk Harnessed Signaling (CHS) technique for parallel high-speed interfaces. The proposed scheme, called Asymmetric Crosstalk Harnessed Signaling (ACHS), provides a robust and consistent eye opening for all the transmitted bits in the interface. The Hadamard matrix employed for CHS encoding has been modified to a non-square format in order to either eliminate the common eigenmode or turn it differential. This in turn results in a signaling scheme that converts a binary data array to a slightly larger signal/interconnect array. The resulting signaling and routing overhead translates into a comparable eye opening across all the bits inside the encoded bus, overcoming the crosstalk sensitivity associated to the common mode present in the original CHS scheme. Both CHS and the proposed ACHS are implemented on a 16-bit source-synchronous bus wired through 3-dimensional interconnect arrangements in a multi-stripline stackup, in order to compare performances in very aggressive crosstalk environments. Simulation results show a consistent eye opening across all data bits when ACHS is applied, rendering a fully functional bus with only 11% routing overhead, against a practically inoperable bus in the CHS case, due to the eye collapse for the common-mode encoded bit.

This paper presents an encoding variation on the Crosstalk-Harnessed Signaling (CHS) technique, aimed towards eliminating the common-mode eigenvector included in the Hadamard matrix for CHS encoding/decoding. This is accomplished by either removing the eigenvector or making it differential by concatenating matrices in a diagonal fashion, or by adding columns to the matrix; this results in a non-square matrix that delivers a larger number of signals to be routed in the interface. Simulation results show the signaling/routing overhead translates in a significantly higher performance for high-speed parallel interfaces with very high routing integration levels.