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In the chip developmental process, bugs are prone to occur, and there is an exponential rise in bug-fixing costs as it advances the design stages. In the past, bugs like Pentium FDIV have led to catastrophes. So, it is highly desirable to find and fix these bugs before tapeout to ensure no functionality is compromised in a chip. Most such fixes are addressed via engineering change orders (ECOs). Typically, every project has multiple ECOs late in the design cycle. It is hard to implement these ECOs manually as manual implementation impacts productivity and time to market (TTM). So, ECOs after RTL freeze must be automated to avoid any such challenges.
Marvell Technologies faced similar challenges, as mentioned in the recent CadenceLIVE Silicon Valley 2022 paper by Deekshith Krishnegowda from Marvell. He spoke about how Conformal ECO Designer adoption helped them to automate their pre-mask ECOs implementation and complete it in 645 –730sec only.
Design teams at Marvell noticed that manually performing ECO was close to impossible. With an automated flow, Marvell could complete complex ECO changes while avoiding human error. Another challenge for the Marvell design team was reducing the tape-out time and using both Conformal ECO and Conformal Logical Equivalence Checking (LEC) flows to help minimize the overall tape-out time. In addition, Conformal ECO offers other benefits that Led Marvell to it.
• Existing formal verification flow can be leveraged with minimal changes for Conformal ECO flow. • Improve productivity by reducing the time taken in the ECO phase. • Enables both pre-mask and post-mask automated ECOs
Marvell has performed multiple ECOs using Conformal’s automated flow on various projects over the past few years. The figure below shows their current Conformal ECO flow:
Below are the steps as followed by Marvell for ECOs automation. Here step 1,2&3 are required to be performed before starting the Conformal ECO flow, and step 4, 5, and 6 are the core of the Conformal ECO flow:
Marvell presented results on various use cases involving combinatorial changes, including:
Both the cases were in the same logic block with the same size, the ECO fixes, and summary of ECO changes is as below:
Implementing design changes is challenging and may lead to tape-out delays, especially with combinatorial circuits. Conformal ECO automates the process and improves productivity by reducing the time taken in the ECO phase. Adopting Conformal ECO Designer at Marvell helped the design team quickly and accurately complete pre-mask ECOs. Conformal can handle complicated ECOs involving combinational and sequential logic changes with ease. In the case of sequential logic ECOs, Conformal seamlessly handles all DFT and scan chain-related challenges.
There are a lot of training materials and rapid adoption kits (RAKs) which can be downloaded from Cadence support. Additionally, please refer to the below topics to learn more about Conformal ECO: