Frequently Asked Questions 

Q:What is CustomSim?
A:CustomSim™ is the unified circuit simulation solution that consists of 3 best-in-class FastSPICE engines: HSIM®, NanoSim® and XA technology.

Q:What is the function of CustomSim?
A:CustomSim performs time-domain transistor-level circuit simulation.

Q:What will happen to HSIM, NanoSim and XA?
A:There is no change to our support and development for HSIM, NanoSim and XA technology. CustomSim combines HSIM, NanoSim and XA technology into a unified solution. The individual simulation technologies that make up CustomSim will continue to be developed and supported as they are today.

Q:Which netlist formats does CustomSim support?
A:CustomSim supports HSPICE®, Spectre & Eldo netlist formats.

Q:Why do you need multiple simulation engines?
A:Individual simulation engines have been optimized for efficiently simulating specific circuit types, e.g., custom digital, memory or analog/mixed-signal blocks. Modern AMS-era designs incorporate many circuit types in a single chip, driving the need for a unified solution that includes all best-in-class circuit simulation technologies. Many man-years of development has gone into the individual engines that have established them as best-in-class.

Q:Why does VCS-CustomSim run faster than “traditional” co-simulation solutions?
A:VCS-CustomSim provides direct kernel integration between the simulation engines for AMS co-simulation. This solution delivers a significant performance advantage over traditional solutions which use Verilog Programming Interface (VPI) integration.

Q:What is the common AMS verification environment?
A:Synopsys’ SpiceExplorer provides a common AMS verification environment that enables designers to launch, monitor and analyze simulation and verification jobs. In addition to transistor-level verification, the environment also supports VCS-CustomSim co-simulation.

Q:How do native circuit checks avoid wasted simulation time?
A:Native circuit checks refer to the portfolio of static and dynamic checks available with the CustomSim solution. The static checks are executed before simulation starts and identify any electrical rule violations. During simulation, the designer can choose which dynamic checks are performed and can elect to terminate simulation should any dynamic violations occur.

Q:How does CustomSim achieve 4x speed-up?
A:New matrix solving technology has been integrated into the CustomSim simulation engines and provides the capability for multi-threading. Designs with large matrices (typically designs with large quantities of post-layout parasitic data with high accuracy requirements) will see the biggest benefit. The new matrix solving technology also provides performance improvements on a single processor core. This technology has been qualified for use with up to eight cores at this time.

Q:How does CustomSim support low-power verification?
A:In addition to accurate transistor-level simulation for current and voltage measurements, CustomSim utilizes native circuit checks to monitor designs for power violations, including excess leakage, missing level shifters and floating gates, which can cause excess current consumption.

Q:Does CustomSim support IEEE 1801 (UPF)?
A:IEEE 1801 (UPF) provides a mechanism to translate power information for digital verification and implementation tools. Since CustomSim is a transistor-level verification solution this information is already understood by the simulator (current and voltage), therefore IEEE 1801 (UPF) power specification input is not needed.

Q:How is CustomSim related to Custom Designer?
A:CustomSim and Galaxy Custom Designer™ are components of Synopsys’ custom design flow. CustomSim is integrated into Custom Designer for circuit simulation.

Q:What is CustomSim-FT?
A:CustomSim-FT provides a transistor-level fast transient analysis capability for high-sensitivity analog blocks. It is the XA technology targeted to simulate designs with up to 30K transistors, regardless of the amount of parasitic elements.

Q:What netlist formats does CustomSim-FT support?
A:CustomSim-FT supports the HSPICE netlist format.

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