nanoFabric Chang Seok Bae

nanoFabric nanoFabric : an array of connect nanoBlocks nanoBlock : logic block that can be progammed to implement Boolean function and switches to route signals Using CAEN (chemically assembled electronic nanotechnology) requires new computer architecture Next: fabrication/architectural implication and overview on the architecture

Fabrication and Architectureal Implications Plausible fabrication process Wires of different types are constructed through chemical self-assembly Aligns groups of wires Silicon-based die Self-assembly (alignment) restriction A post-fabrication configuration Bypassing defect density

Fabrication and Architectureal Implications (cont) Two-terminal device (diode-resistor logic) Three-terminal device is unsuitable with inexpensive chemical assembly No inverter: output and its complement Signal restoration and registers Lack of transistor CMOS: density problem and speed down Molecular latch: composed of a wire with two inline NDR (negative difference registers) at either end

NanoFabric architecture nanoBlock nanoBlock connectivity Scalability Defect Tolerance Configuration

nanoBlock Fundamental unit MLA (molecular logic array) : functionality of block Latches I/O area: connect the nanoBlock to its neighbors

nanoBlock (cont) MLA Two orthogonal sets of wires: when configured to be “on”, act as diodes Benefit: construted by direct assembly Drawback: signal degrading, so molecular latch is used

nanoBlock Connectivity Fabrication constrain bring each side of block to have inputs or output but not both: one diagonal Switch block: input/output overlap

Scalability Arrangement of clusters and long-wires Routability of netlists as the number of components increasing Configuration time to be remained due to parallel configuration

Defect Tolerance Defect-tolerant nature Regularity: choose where particular function is implemented Configurability: pick one component (nanowire, parts of nanoBlock) which implements particular circuit Fine-grained nature: reduce the impact of a defect to a small portion of the fabric, which enriches interconnection overhead Key difficulty: impossible to test the individual components in isolation Teramac: inconjuction with an outside host to test itself

Defect Tolerance (cont) Defect mapping process Phase I: no known fault-free regions Basic tester implemented in CMOS Host computer configures testers Phase II: After a sufficient number of functioning resources discovered Already tested area of the fabric acts as a host for testing the remainder For very large devices, many parallel independent device used

Configuration Molecular switch : high voltage outside the normal operating range Configuration Fabric scale: Fabric is design so that clusters can be programmed in parallel Cluster scale: configuring one nanoBlock per cluster due to CMOS overhead nanoBlock scale: Accessing each nanowire separately not in space but in time dimension

SAM simulation To exploit the advantage of nanoFabric, SAM (a split-phase abstract machines) is proposed and simulated. Comment: this simulation is approached at highest level away from the circuit constraints.

Conclusion Even though this approach exploit the parallel nature of chemical assembly, fine- grained style brings high complexity of configuration to implement functionality or fault tolerance There are still many challenges left in creating functional computing device