XDWM: A 2D Domain Wall Memory

Domain-Wall Memory (DWM) structures typically bundle nanowires shifted together for parallel access. Ironically, this organization does not allow the natural shifting of DWM to realize
logical shifting
within data elements. We describe a novel 2-D DWM cross-point (X-Cell) that allows two individual nanowires placed orthogonally to share the X-Cell. Each nanowire can operate independently while sharing the value at the X-Cell. Using X-Cells, we propose an orthogonal nanowire in the Y dimension overlaid on a bundle of X dimension nanowires for a cross-DWM or XDWM. We demonstrate that the bundle shifts correctly in the X-Direction, and that data can be logically shifted in the Y-direction providing novel data movement and supporting processing-in-memory. We conducted studies on the requirements for physical cell dimensions and shift currents for XDWM. Due to the non-standard domain, our micro-magnetic studies demonstrate that XDWM introduces a shift current penalty of 6.25% while shifting happens in one nanowire compared to a standard nanowire. We also demonstrate correct shifting using nanowire bundles in both the X- and Y- dimensions. Using magnetic simulation to derive the values for SPICE simulation we show the maximum leakage current between nanowires when shifting the bundle together is
$\le$
3% indicating that sneak paths are not problematic for XDWM.