Avoidance proposed as solution to 90-nm problems

Just how this might be accomplished was a matter of some debate. Vasishta, for his part, recommended a correct-by-design approach from the very beginning of floor planning and RTL coding. "Placement and global r outing have to be comprehended during the RTL-coding process," he argued. "With all the variables that have to be considered, it's simply too complex to deal with at the gate level."

Ted Vucurevich, senior vice president and chief technology officer at Cadence Design Systems Inc., agreed. "At 90 nm the design technology has to become wire-centric, not transistor-centric," he said. "You have to look at the wiring topology and the layer assignment early on in the process."

The notion that RTL must be a description of the wiring, not simply an expression of the logic, recurred during the panel. It has also been voiced frequently by design teams (not represented on the panel) that are working with 130-nm designs.

Front-end design

Later in the discussion, Vucurevich returned to the theme, describing his notion of the correct front end for a 90-nm flow. "You need to begin with the construction of a functional virtual prototype," he said. "It's not possible to deal with op timization of mask-level designs at today's level of complexity. You have to deal with them at the beginning, in the virtual prototype."

He went on to describe that prototype as a view of the RTL that is placed and routed, at least at the global-routes level, based on fast algorithms that yield a conservative approximation of the final routing. The point is to find a level of abstraction at which it is possible to inspect the estimated placement and routing for obvious risks of signal-integrity or power issues, without having to do a detailed route.

It has been suggested that the pursuit of this virtual prototype will lead to code inspection tools for RTL that look not for logic errors but for structures that inherently create routing issues. Those tools would work in concert with tools that would estimate footprint, placement and major routes directly from the RTL.