Variety MX for Embedded Memories Statistical Timing Model Generator

Variety MX, from Altos Design Automation, is a fast and accurate statistical timing model generator for embedded memories. Variety MX generates instance-specific Liberty models for use by Cadence’s Encounter Timing System GXL, Extreme DA’s Goldtimetm, and Synopsys PrimeTime VX. Variety MX is able to characterize memory sizes that cannot be adequately simulated using brute Monte Carlo methods or even with fast sampling techniques. Variety MX is available now.

Variety MX leverages technology from Liberate MX to perform “automatic probing” and “dynamic partitioning” to address the runtime and accuracy challenges that arise from statistical characterization of large macro blocks that often comprise millions of transistors. Since a “dynamic partition” represents just the active critical path for a given timing arc and is typically only a few hundred transistors, it can be characterized using similar techniques as those deployed for statistical characterization of standard cells. This includes characterizing the sensitivity of both delay and timing constraints to global (systematic) and local (random) process variations.

Variety MX uses “dynamic partitioning”, i.e. partitioning based on a full chip simulation of a circuit using a “fast-spice” simulator. This has the advantage of being able to account for effects common at advanced process nodes such as interconnect coupling, power supply gating and transistor stress. As “dynamic partitions” are small, they can be characterized by a “true-spice” simulator providing highly accurate results. Without partitioning, nearly all memory instances are too large to be simulated with traditional or fast Monte Carlo methods rendering statistical characterization impossible.

To account for the impact of process variation Variety MX leverages Altos’ proprietary “inside view” methods that reduce the overhead of local (random) variation characterization to 3X or less of nominal characterization, in contrast to Monte Carlo simulation which will be at least two or three orders of magnitude slower. The statistical library models generated by Variety MX are consistent with those created by Varietytm for standard cells. This includes support for statistical current source model formats, CCS VA from Synopsys and S-ECSM from Cadence.

Variety MX supports multiple “fast-spice” simulators including Synopsys CustomSim (HSIM, NanoSim and XA), Mentor’s ADiT and Cadence’s Virtuoso UltraSim Full Chip Simulator for “fast-spice”. Synopsys Hspice, Cadence’s Spectre, Mentor’s Eldo and Altos’ Alspice are all supported for “true-spice” simulation.

More info: Altos Design Automation