Magma takes floorplanning to another level, so to speak

Floorplanning for SoCs seems to be a subject rife with paradox. On one hand, the exercise of iteratively refining the chip’s floorplan seems to be the axel that holds hierarchical design together. On the other hand, improving the floorplan always seems to require one more level of detail than is currently available to the planners. So invariably, the floorplan is based on estimates of the size, shape, and timing of the blocks, and its quality depends heavily on the experience of the senior design staff.

Magma Design Automation is going to try to automate and streamline this iterative process a bit with a new comprehensive floorplanning tool they are calling Hydra. (The name is apparently in honor of the many-headed serpent dispatched by Hercules, which would eventually be the indirect agent of that hero’s demise. The exact metaphor here is not quite clear, but ominous enough, given the difficulties design teams have had with floorplanning.)

A number of points make Hydra unique, according to Magma product director Sanjay Bali. One of these is that Hydra is what Bali describes as automated-interactive. Some of Hydra’s functions are in fact automated synthesis: of block partitions and shapes, macro placements, power grids and top-level clock trees, for instance. Other functions are intended to be used interactively by the floor-planning team. Another significant point is that Hydra uses common file formats with, and in some cases simply uses, other placement, timing, and synthesis engines in the Vortex flow. This should relieve design teams of having to translate files between planning and implementation flows, and should improve convergence of the floorplan onto the final placement. But Bali is quick to point out that Hydra can be used as a stand-alone tool independent of the Talus flow, also.

Hydra works with the design team through iterative refinement of the plan. It starts early in design, providing automated block shaping and location based on known pad and pin locations and other black-box data about the blocks. This process generates pin, power-grid, and very early timing information that can be pushed down the hierarchy into the block planning processes.

Next, Hydra can automatically generate primary floorplans, including creation of voltage domains, pin and pad placement, and gradual definition of the inner shapes of the blocks. At this point the tool can work interactively with designers to absorb, for example, information about the shape and location of hard IP blocks. The tool also creates partitions in the logical hierarchy automatically, impacting pin placement and timing as things get laid out.

The information thus generated is passed as constraints to a shaping engine, which shapes the partitions that have been defined on the logical hierarchy, and also places and legalizes macros with a shape- and congestion-aware auto-placement engine. With this process complete, Hydra can automatically generate power grids and clock tree hierarchy. At this point the tool can generate production-quality top-level clock structures and prototype-quality block-level clock trees, Bali says. Hydra can also work with Magma’s package co-design tools on placing bumps, I/O cells, and redistribution layer information along with the emerging floor plan.

A key part of the process now, according to Bali, is budgeting. The information Hydra has generated in the process of constructing the floorplan gets pushed down to the block level as timing budgets and other constraints for the block implementation tools. As blocks are implemented, Hydra allows abstraction of detailed block designs back into the floorplanning process to refine the emerging picture of the full chip. By maintaining relative floorplanning constraints, the tool can incorporate changes without disrupting the rest of the plan.Thus, Magma claims, the tool provides a single cockpit for managing an hierarchical design from early exploration through implementation and into the final assembly process. Bali says that Hydra is unique in its ability to serve the team from planning through prototyping, and on to the preparation of the production-ready floorplan.

In this light, perhaps we have the metaphor backward. The name Hydra should perhaps refer not to the tool itself, but to the tangle of interacting—and potentially toxic—constraints and requirements that the tool gradually resolves as the design flow moves forward. From here, we can only trust that the design team, unlike Hercules, shall avoid dicey encounters with centaurs and thus shall escape any terminally painful aftereffects from the floorplanning process.