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About a year ago, we introduced the Spectre X simulator in the SPECTRE 19.1 base release. Since then, many enhancements have been made in Spectre X in the subsequent SPECTRE 19.1 ISR releases. The SPECTRE 20.1 release, coming out in early October 2020, also contains some major enhancements related to Spectre X. In this blog, I'll provide an overview of the updates related to Spectre X and the enhancements that have been delivered in the SPECTRE 19.1 ISR releases.
Spectre X Overview
Spectre X targets the most challenging simulation problems, including advanced node designs with complex FinFET (and other) device models, and RC-dominated post-layout designs. It includes the following two technologies:
Spectre X provides performance and capacity that is much improved compared to Spectre APS, as shown below. In addition, it significantly simplifies the Spectre use model, thereby making the Spectre APS tuning options obsolete.
You can find detailed information about the Spectre X use model, the transition from Spectre APS to Spectre X, and the ADE Explorer GUI support for Spectre X in the Introducing Spectre X application note.
Performance Comparison with Spectre APS
A few months back, I simulated a pre- and post-layout version of an ADC design with both Spectre APS and Spectre X to evaluate the performance of Spectre X when using eight cores. The design contained 300k BSIMCMG devices. The pre-layout version had 2M estimated capacitors, while the post-layout version contained 15M parasitic capacitors (mostly coupling caps) and 8M resistors. While the accuracy was confirmed by the designer, the performance comparison on the same machine with the same number of cores showed the following gains.
Spectre APS (8 core)
Spectre X (8 core)
More recently, I performed a direct EMIR simulation of a large 28nm memory design. This design was large enough to see significant performance gains from the Spectre X high core count simulation. With a 32 core Spectre X simulation, I was able to speed up the simulation by 7.2x down to an overnight run, with the same accuracy as Spectre APS. The following table shows the performance comparison:
1.2M MOS, 40M R, 20M C
Spectre APS 8T
Spectre X 8T
Spectre X 32T
Power Net EMIR analysis
1d 7h (2.1x)
Both the above designs were in the sweet spot of the Spectre X technology. Although Spectre X also provides performance gains on smaller and legacy node designs, these performance gains may be less compared to the gains shown above.
Spectre X Enhancements in SPECTRE 19.1 ISR Releases
When Spectre X was first released in the SPECTRE 19.1 base release, it did not support a few Spectre flows and features. Support for these flows and features was added in the subsequent SPECTRE 19.1 ISR releases. For example, in SPECTRE 19.1 ISR2, we added support for EMIR and aging analysis, and in SPECTRE 19.1 ISR10, we added support for the Spectre dcmatch, acmatch, sensitivity and pole zero analyses.
In addition, significant performance, capacity, and accuracy enhancements were made in Spectre X in the SPECTRE 19.1 ISR releases. Besides many design and technology-specific enhancements, the key changes were: Reduced LX and VX mode peak memory usage in SPECTRE 19.1 ISR3, post-layout simulation accuracy improvements in SPECTRE 19.1 ISR8, VX performance improvements in SPECTRE 19.1 ISR9, and CX mode accuracy improvements in the SPECTRE 19.1 ISR10 releases.
We recommend that you use the latest Spectre 19.1 ISR release to take advantage of the recently delivered simulation technologies.
Spectre X Enhancements in the SPECTRE 20.1 Release
In the SPECTRE 20.1 release, you'll be able to use Spectre X in Spectre RF analyses. In addition, you'll be able to run a distributed harmonic balance analysis using the Spectre X solver. The Spectre X solver will also be supported in Spectre MS. Watch out for the SPECTRE 20.1 release announcement blog for more information.
You may also contact your Cadence support AE for guidance.
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About Spectre Tech Tips
Spectre Tech Tips is a blog series aimed at exploring the capabilities and potential of Spectre®. In addition to providing insight into the useful features and enhancements in Spectre, this series broadcasts the voice of different bloggers and experts, who share their knowledge and experience on all things related to Spectre. Enter your email address in the Subscriptions box and click SUBSCRIBE NOW to receive notifications about our latest Spectre Tech Tips posts.