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Expert Interviews: Jasper’s Lawrence Loh: IP Power Specs

LPD got to speak briefly with Lawrence Loh of Jasper Design Automation about IP power specifications recently.  Here’s what we learned.

Q: “What can IP providers do to provide better models to more accurately represent power in various operating states?”

SOCs today are made from IP, they aren’t designed from scratch.  Most of the power description is done at the SoC level though.  You rarely see power domain descriptions for IPs.
There are two types of power models that are very important to provide for IP.  Power estimation is not just a number.  It’s about what determining what usage scenarios use what power.  The first set of models is built by looking at which signals are switching during a particular functional behavior of the IP. Then power-estimation for each of these behaviors is performed. With this model, the SOC team can perform its own power estimation based on which and how often certain functional behaviors of these IPs are used.
The second set of models is the functional model that maps the behavior of the SoC in terms of integrated functionality.  These models need to accurately model the behavior of the IP, not just for normal functionalities, but also for power-up and down behavior. The SOC team will then able to verify the overall SOC functionalities including power-sequencing and other low-power behavior.

SOCs today are made from IP, they aren’t designed from scratch.  Most of the power description is done at the SoC level though.  You rarely see power domain descriptions for IPs.  There are two types of power models that are very important to provide for IP.  Power estimation is not just a number.  It’s about what determining what usage scenarios use what power.  The first set of models is built by looking at which signals are switching during a particular functional behavior of the IP. Then power-estimation for each of these behaviors is performed. With this model, the SOC team can perform its own power estimation based on which and how often certain functional behaviors of these IPs are used.  The second set of models is the functional model that maps the behavior of the SoC in terms of integrated functionality.  These models need to accurately model the behavior of the IP, not just for normal functionalities, but also for power-up and down behavior. The SOC team will then able to verify the overall SOC functionalities including power-sequencing and other low-power behavior.

Q:  Who is the customer of the power description information?

The SoC team usually has a group that is specifically in charge of low power. They determine what power each IP block uses, compare this with the power budget they have, and determine how to partition the IP into different power domains to accomplish their goals. Once the power domains are determined, they will need to define a proper power sequence to enable and disable power for each domain.  The next level of customers for IP power specifications are the people who do the implementation.  They create a file alongside the RTL code that describes how IP blocks connect to each other.  They try to include enough information so that if, for example, blocks that were initially connected with each other directly are placed in different domains, it will be apparent where rails need to be placed to isolate the new domains from each other.  These are usually people who write in the proprietary or standard format that describes the power.  Finally, there are the verification people who need to make sure that the different power behaviors work as expected.   With so many different groups of people that need to work with the power domains it’s important to have a way to capture this information.

From the solution space point of view, obviously many vendors are providing solution to different aspects of low power engineering projects.  Having a power specification language that describes power consumption, power domains and interconnects allows different tools to enter into the flow.  Low power is a big aspect of SoC design projects spanning many activities and solution spaces.   A power specification language gives different vendors a way to integrate their tools together so that they can implement a complete low power solution.  There are some standards around and standards have advantages and disadvantages, but the advantages are more universal.  IPXACT is one way to standardize. SystemRDL is another.  The jury is still out on what format is the best.

Lawrence Loh, Vice President of Worldwide Applications Engineering, Jasper Design
Lawrence Loh holds overall management responsibility for the company’s applications engineering and methodology development. Loh has been with the company since 2002, and was formerly Jasper’s Director of Application Engineering. He holds four U.S. patents on formal technologies. His prior experience includes verification and emulation engineering for MIPS, and verification manager for Infineon’s successful LAN Business Unit. Loh holds a BSEE from California Polytechnic State University and an MSEE from San Diego State.

Lawrence Loh, Vice President of Worldwide Applications Engineering, Jasper DesignLawrence Loh holds overall management responsibility for the company’s applications engineering and methodology development. Loh has been with the company since 2002, and was formerly Jasper’s Director of Application Engineering. He holds four U.S. patents on formal technologies. His prior experience includes verification and emulation engineering for MIPS, and verification manager for Infineon’s successful LAN Business Unit. Loh holds a BSEE from California Polytechnic State University and an MSEE from San Diego State.

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