Update for OpenLANE Timing Issues and MPW-2 / 3
Jeff
Hello everyone,
With the deadline for MPW-3 coming up, we wanted to recap and clarify a few items related to the MPW-2 and MPW-3 shuttles.
OPENLANE
The cause of the timing issues on MPW-ONE has been identified and updates to OpenLANE have been made to correct for it. These changes include changes to the design flow to synthesize the clock tree as well as to ensure that timing errors are identified and either corrected or the design flow is stopped as a result.
For users working on designs, we recommend that you update to the latest version of OpenLane and rerun hardening your project.
MPW-2
The MPW-2 shuttle was caught before going to fabrication. Caravel is being updated to correct for the timing violations in the clock tree. The shuttle timing will be delayed as a result.
People who used OpenLane for hardening digital projects will be concerned about timing issues in their projects on the MPW-2 shuttle. We share that concern and, as such, we will be posting instructions on how to check your design. We are working to collect more information and we ask anyone who has run the check to report their results back to us.
We will also be scheduling a live session to provide an overview of how to close timing violations using OpenLane with a Q&A.
If you are interested in learning more about timing violations, Matt Venn posted a great explanation in his latest video ( MPW1 silicon arrived! What went wrong? ).
MPW-3
MPW-3 will have an updated design for Caravel that corrects for the timing issue. It will also contain a number of additional improvements to allow fail-safe operations. This includes changes to the IO configuration to allow users to access and configure the IO pads without needing the Management processor in Caravel.
For MPW-3, several new updates have been made to the process including changes to mpw-precheck as well as a new step following precheck to execute the tapeout job for your project. The latter does all the final steps to integrate your project with Caravel, and runs fill generation and final metal density checks before your layout is submitted to the foundry. This change not only puts you in the driver's seat and allows you to know your project is ready to go; but also greatly streamlines and expedites the delivery of shuttles to the foundry which shrinks and improves the predictability for time to get parts back.
It is important to note, the tapeout job uses the commit id from the selected precheck run. This is the version of the project that goes on the shuttle. You can find the commit id in the log for the precheck job.
As a reminder, the deadline for submission for MPW-3 is this Friday, October 29 @ 11:59pm PST. You need to complete a successful precheck along with a successful tapeout job prior to the deadline. You may continue to update your project after running a tapeout job, but you will need to rerun both precheck and tapeout with the final design updates before the deadline.
While working through these challenges can be painful, we are reminded that this community is doing things that no one ever thought was possible. The learning we are getting from this first shuttle is setting the foundation for our future successes over the next iterations. Thank you again for your continued support and commitment to bringing open source and community collaboration to chip design.
Thank you.
The Efabless Team