Powering Up Power Analysis
by Bryon Moyer
May 08, 2012 at 1:58 PM
Apache has just released their latest RedHawk version, RedHawk-3DX. In it they’ve focused on areas of growing importance for power: 3D ICs, working at the RTL level, and scaling up the size of sub-20-nm designs.
Power is of particular concern for 3D ICs because of the fact that a “cube” of silicon is much harder to cool than a plane. And it’s not a monolithic cube; it’s a bunch of interconnected planes that can become detached if you’re not careful. Even the TSVs can be problematic.
They’ve allowed concurrent analysis of each die and the interconnects and TSVs, with the ability to view each piece separately to see where the hot spots and physical stresses are. And they’re not just calculating heat or power; they are determining physical stresses as well. They do this with models, not with full finite-element (FE) analysis, although the models themselves may be created through more accurate FE methods.
RTL-level analysis is important for debug reasons. Most analysis is now done at the gate level, but most designers won’t have vectors at the gate level; only at the RTL level. And if problems are found at the gate level, it’s hard to debug them since that’s not the level designers work at.
So they now have the logic propagation technology in place to support RTL-level analysis with vector inputs. Vectorless analysis is also possible at the RTL and global levels; this is where you specify approximate transition frequencies on pins, and then probabilities (instead of actual events) are propagated to perform the analysis.
For scaling purposes, they have enabled hierarchical analysis, allowing different blocks to be analyzed independently, creating something akin to a bus-function model, where the periphery of the block is accurate while the internals aren’t. That way you can plug the blocks together to see how they interact and still complete the analysis in a reasonable time. A full chip can thus be analyzed with blocks done with or without vectors, at the gate or RTL level; you can mix and match.
There are lots of other details that you can get to via their announcement.