Simultaneous Floorplan and Buffer-Block Optimization

Abstract

Abstract-As technology advances and the number of interconnections among modules rapidly increases, timing closure, and design convergence are the most important concerns. Hence, it is desirable to consider interconnect optimization as early as possible. Previous work for this issue can be classified into two directions: wire planning and buffer-block planning for interconnect-driven floorplanning. Wire planning for interconnect-driven floorplanning does not consider buffer insertion, and buffer-block planning for interconnect-driven floorplanning cannot overcome the limitation of a bad initial floorplan. In this paper, we first address simultaneous floorplanning and buffer-block planning (i.e., integrating buffer-block planning into floorplanning) for interconnect optimization. We adopt simulated annealing to refine a floorplan so that buffers can be inserted more effectively. In each iteration, we construct a routing tree for each net, allocate buffers for all nets, introduce corresponding buffer blocks into the intermediate floorplan, and invoke Lagrangian relaxation to optimize area and satisfy timing requirements. Further, in order to reduce the problem size, we present supermodule partitioning which partitions modules into supermodules. Experimental results show that our method of integrating buffer-block planning into floorplanning can significantly improve the interconnect delay and reduce the number of buffers needed. Based on a set of MCNC benchmark circuits, our approach achieves an average success rate of 86.1% of nets meeting timing constraints, inserts only 272 buffers on average, and consumes an average extra area of only 0.28% over the given floorplan, compared with the average success rate of 62.6%, 1123 buffers, and extra area of 1.05% resulted from a famous recent work presented at ICCAD'99.

Practical Problems in VLSI Physical Design Automation

“…The authors of [Jiang et al, 2004] performed simultaneous floorplanning and buffer block planning for more rigorous interconnect planning. In order to accurately compute the size and location of buffer blocks, the authors performed global routing for all nets using the AHHK heuristic .…”

A stochastic power-supply noise reduction technique using max-flow algorithm and decoupling capacitance

“…The quantity avg is the average cost change of a random sequence of moves, and P is initial probability of accepting uphill moves. avg and P are set to 40 and 1.1 in our work respectively [13]. For simplifying the floorplan problems and focus on the power supply noise suppression, we analysis slicing floorplan with only hard rectangular blocks (not soft blocks with L-shape or Z-shape).…”

Improved predictability, timing yield and power consumption using hierarchical highways-on-chip planning methodology

“…Jiang et al [9] also presented a floorplanning algorithm with buffer block planning. They used simulated annealing to find the best routing tree considering buffer blocks.…”