In the context of physical synthesis, large-scale standard-cell placement algorithms must facilitate incremental changes to layout, both local and global. In particular, flexible gate sizing, net buffering and detail placement require a certain amount of unused space in every region of the die. The need for "local" whitespace is further emphasized by temperature and power-density limits. Another requirement, the stability of placement results from run to run, is important to the convergence of physical synthesis loops. Indeed, logic resynthesis targetting local congestion in a given placement or particular critical paths may be irrelevant for another placement produced by the same or a different layout tool.In this work we offer solutions to the above problems. We show how to tie the results of a placer to a previously existing placement, and yet leave room for optimization. In our experiments this technique produces placements with similar congestion maps. We also show how to trade-off wirelength for routability by manipulating whitespace. Empirically, our techniques improve circuit delay of sparse layouts in conjunction with physical synthesis.In the context of earlier proposed techniques for mixed-size placement [2], we tune a state-of-the-art recursive bisection placer to better handle regular netlists that offer a convenient way to represent memories, datapaths and random-logic IP blocks. These modifications and better whitespace distribution improve results on recent mixed-size placement benchmarks.
Abstract. We describe fully polynomial time approximation schemes for generalized multicommodity flow problems arising in VLSI applications such as Global Routing via Buffer Blocks (GRBB). We extend Fleischer's improvement [7] of Garg and Könemann [8] fully polynomial time approximation scheme for edge capacitated multicommodity flows to multiterminal multicommodity flows in graphs with capacities on vertices and subsets of vertices. In addition, our problem formulations observe upper bounds and parity constraints on the number of vertices on any source-to-sink path. Unlike previous works on the GRBB problem [5,17], our algorithms can take into account (i) multiterminal nets, (ii) simultaneous buffered routing and compaction, and (iii) buffer libraries. Our method outperforms existing algorithms for the problem and has been validated on top-level layouts extracted from a recent high-end microprocessor design.
Abstract-As technology scales, interconnect-centric design flows become imperative for achieving timing closure. Preplanning buffers and wires in the layout is critical for such flows. Both buffers and wires must be considered simultaneously, since wire routes determine buffer requirements and buffer locations constrain the wire routes. In contrast to recently proposed buffer-block planning approaches, our novel design methodology distributes a set of buffer sites throughout the design. This allows one to use a tile graph to abstract the buffer planning problem and simultaneously address wire planning. We present a four-stage heuristic called resource allocation for buffer and interconnect distribution for resource allocation that includes a new, efficient technique for buffer insertion using a length-based constraint. Extensive experiments validate the effectiveness of this approach.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.